I just finished my first play-through of BG3 Chapter 1 and I must say, this game is beautiful!
It still has a long road ahead, both in fixing bugs/crashes and improving UI/mechanics, but I think this game has amazing potential!

I compiled a list of all the things I think can be improved upon. The list does not contain bugs, only feedback on game mechanics and how I think they can be improved (I will get to bugs and bug-reporting later).
I'm not super familiar with D&D 5e rules, so take some of my suggestions with a pinch of salt. Here is my list, by category hope it helps:

- Dip Torch should be a tooltip or something because its easy to miss
- Talking with animals: I didn't even notice there's a potion that lets me do it until I was 99% through chapter 1. You could add a hint in loading screen, and or add a dialogue/quest that requires it in druid grove.
- Crafting is not clear at all right now, I saw a few places where I could craft but had no idea how or why I should.
- Barter mode: show a tooltip that the player needs to press the button to get an equal offer from the merchant.
- Spell casting and concentration rules are not clear enough to anyone not familiar with 5e rules.
- Make the causes for advantage/disadvantage on attacks clearer. It took me a long while before I figured out that height/hiding/backstabbing/... all play an important role in combat.

Character Creation
- Would be nice to be able to see all cosmetic (hair/face/...) options without cycling through them. You could, add a menu which shows all cosmetic options and how they would look
- No alignments

- No space hamsters! It's not Baldure's Gate without a space hamster, sorry Larian, but you need Boo.
- Too serious / no humor: would be nice to break the ominous "I have a brain-eating worm in my head" vibe by spicing it up with jokes or colorful characters.
- Make racism great again: player race doesn't have enough impact on dialogues, for example, when playing Drow I expected everyone to go "OMG Drow! Kill it with fire!" but the actual response was either mild or non-existent. Even the Grand-Duke quest, where they were literally attacked by Drow mere moments ago... would be "nice" to get more hostile reactions for Drow/Tiefling/Githyanki, or make jokes about Halfling/Dwarf by calling them "short stuff" or Elf "long-ears", etc...
- Make Disguise-Self an actual thing you need for some races in certain areas, for example a Drow should not be able to walk freely in a human settlement.
- Sense of urgency with Ceromorphosis vs Rest: Make it clearer sooner that it's ok to rest and you won't turn into a mind-flayer if you do. I played through most of Chapter 1 with almost no rest, partially because I didn't want to turn into a mind-flayer.
- Fast Travel + Long Rest from anywhere breaks immersion: being able to to fast-travel/go-to-camp in an instant when I'm in a dungeon/underdark and go right back, breaks the awesome feeling that I'm in a dungeon and should be extra careful. BG2 for example, did this perfectly by limiting player rest and/or interrupting it with monsters more frequently (no fast-travel then).
- Rest can't be interrupted by monsters, it should be, unless you're resting in a safe area like an inn in a town.
- Day/Night cycle and timed quests could be awesome: for example help Timmy before he turns into a ghoul, certain monsters more active at day/night, etc...
- Character Good/Evil/Neutral alignments have no impact and seem to not even exist in game, they should.
- Add a "hardcore" game-mode that limits save/load spamming and add a difficulty setting.

- In-game Bug Report: It would make it a lot easier to report bugs if there was an in-game button that sends a bug-report to Larian, and it would allow you to get a lot of extra data like: screenshot, combat log, computer info, etc... if you want the community to report these issues you should make it easier for us. Right now its really hard to properly report everything because you need to: (1) keep track of all the bugs+screenshots while you play (2) Exit the game (3) Open forums and search if the issues already exists or not (4) Post a New Thread because you missed another thread that talks about the bug you're having (5) Read complaint threads about duplicate threads... and repeat.
- Spell descriptions should include: duration, current DC, how leveling up affects them, spell components (somatic/verbal/material)
- Examining a creature should list his known Saving Throws stats not just his ability scores.
- Add a detailed description to spells in spellbook with flavor text and maybe example animations (example animations would be super cool)
- Hotbar is a total mess and can't be re-arranged easily. BG2 handled it nicely by having quick-slots for items/spells
- Quests window should be able to toggle on/off completed quests and maybe add filters for quest areas
- Quest Markers should go away when quest is completed and it would be nice to be able to turn them on/off for specific quests
- Scroll-bars on menus are way to thin, took me several minutes to even notice they are there
- Inventory management is a chore: I think that having a party-inventory instead of a per-character inventory would make things much easier, I strongly dislike having to manage weight issues among my characters and/or remembering which character has the item I'm looking for... also make a "compact" button to automatically group items together.
- Almost every crate/pot/box/chest/corpse is lootable even if it's empty, it would be nice if they weren't so I wouldn't waste time trying to loot them (I like looting everything in sight because I'm greedy that way).
- Disable being able to pick up crates/pots/boxes/chests/... Move them around yes, put them in inventory please no.
- Wizard should not be able to learn Cleric spells from scrolls, but they can.
- Combat log doesn't progress automatically and has to be scrolled manually
- Combat log should include dialogue, in case you missed something like a spontaneous comment about finding a key / switch / funny comment / etc...

- Hide as a Bonus Action is overpowered: Hiding in combat should be a lot more difficult. Right now, my rouge can just lay far back and Sneak Attack every single round from the shadows which is completely overpowered in my opinion. Either make the DC to hide a lot harder in combat, or don't allow it unless you have a special ability or use a spell, like invisibility.
- Jump/Disengage as a Bonus Action is overpowered: Jump/Disengage totally negates Attack of Opportunity and makes melee combat the worst possible choice. You can also jump over any enemy to backstab it, even if its much taller than you, like Minotaur for example. I suggest making Jump/Disengage an action instead of Bonus Action and make it not possible to jump over tall enemies.
- Shove is overpowered: Make shoving harder and the distance shorter, or even make them prone instead of throwing them off. It should be near impossible for my 8 strength Wizard to shove anything, but right now he can throw enemies half-way across the map like the freaking Hulk... You could also make the distance dependent on the dice, for example if I rolled a Nat 20, maybe my Wizard deserves to be the Hulk for this round, or if I rolled a Nat1 make me fall on my face or add an "unbalanced" condition that adds advantage to enemy attacks this round. Additionally, you should not be able to Shove any creature that is a lot bigger than you.
- King of the Hill: every battle I fought turned into a ranged fight where I'm trying to gain the upper ground and shove my opponents off it, making every other tactic inferior... why even waste spell-slots if I can just do ranged and shove everything.
- Barrels/Mines should show explosion radius when targeted (before attack)
- Traps perception checks should be triggered sooner, every single time the perception check would trigger when I'm literally right on top of the trap, which is really frustrating.
- Make it clearer how an attack would affect a surface when targeted - write in bold "Ignite surface" or something
- If any of my characters are currently not in combat, combat will pause on one of my characters until the rest arrive. This breaks immersion, I suggest having the other characters also act in turn-based mode, so if they are all the way across the map it should take them several combat rounds to get there instead of combat just pausing until they do.
- I think that some items in the game are completely overpowered, such as: Warped Headband of Intellect or the The Sapphire Spark. Bring the Nerf hammer!

Keep up the good work Larian, I know you can make BG3 even better smile