Hi DasSchn1tzel. Thanks for your detailed feedback; it's good to have some from people coming from different backgrounds.

Intro
You're right that the tutorial needs work. There are lots of things that are not explained in the current tutorial, and it's relatively easy to miss the tutorial windows that do pop up. As a frequent pen and paper D&D player, even I had trouble figuring some things out.
It would be nice if, on the character creation screen, you could scroll down to see what abilities each class gets at following levels.
Larian also needs to improve the explanation of stats and change the default starting arrays to be more player friendly (more even values, more optimal distributions. Or failing that, remove the default arrays, start every stat at 8, and make the player manually add all the points.)

UI
Yep, I agree with everything you said here, and so do many players based on other forum posts.

Dialogue Skill Checks
This is somewhat just a feature of D&D 5e. A level 1-3 character with proficiency in a skill and a high stat for it(16) will have a +5 in that skill. Average characters have somewhere from a +0 to +3 in a random skill, meaning that your "expert ranger" only has a bonus of (5-2=)3 more than a typical character. This comes out to succeeding 15% more of the time, which is really not much compared to the randomness of a d20.
-A suggested fix for this is for Larian to implement more "Passive Checks", where you don't roll, but instead use your Passive Skill Score = 10+skill bonus, which would mean your ranger would always succeed at a DC 15 nature check whereas other characters would always fail.
-Another suggestion is to make heavy use of Guidance in the game. This is a cantrip spell (it can be cast infinitely) so someone can cast it on yourself before any and every dialogue. This adds 1d4 to your skill checks, which is not insignificant.
-Another suggestion is for Larian to add more stages of success/failure instead of all-or-nothing. E.g., if you fail by <5 of the DC, something only mildly bad happens. Whereas if you fail by >5, something worse happens.

Dialogue Options
You can just tell Shadowheart to leave your group :P
But yeah, I don't think anyone would complain if we had more dialogue options. Especially in response to the companion's snarkiness.

Balancing
Larian has already reduced the effects of surfaces (I believe they eliminated surface creation from cantrips??), but yes I also hope they make acid arrows and alchemist fire flasks etc less prevalent.
Enemy Strength: Without knowing the exact build of your party and your combat tactics, I can't really comment on this. Some enemies are supposed to be stronger than any individual PC. It is only through a party that a one can overcome such a threat.

RNG is a big discussion in the forums. Some arguing that the current randomness is fine, some saying there is way too much failure, some even saying that Larian has implemented a rng that is weighted toward low numbers. Larian has said they're looking into using weighted die rolls of some kind, but at this point it is very unknown how that will be implemented.


Reloading
I have moderately extensive PnP D&D experience. TPK's (total party kills) happen very rarely. Even single character death happens decently infrequently, especially in this version of D&D. In most campaigns I have played in, <2 characters die throughout the full campaign. However, BG3 is a video game and has reloading, whereas pen and paper D&D does not. I would be very unhappy/bored with a BG3 video game where my characters never died and I never had to reload. I want the challenge, and the ability to reload means that the challenge can be upped.
On a normal difficulty, I'd expect to have to reload approximately once between each boss fight. So in BG3 EA, in a first playthrough especially, it wouldn't be unreasonable to reload for ~2-5 encounters (depending on your playthrough choices). Thinking back, I reloaded: spider fight (2x), Grove Gate seige (1x), gith (1x), random fire trap (1x), and then maybe 1-2 more times I can't remember. So I reloaded 4-5 encounters, some multiple times.

To be honest, given your 0 experience with BG and D&D, I think expecting to start right away with an "ironman" mode was probably too ambitious. Especially since (I believe this was only mentioned verbally by Larian studios during a multiple hour long interview), the EA is supposed to be somewhere between "normal" and "hard" difficulties.
So yes, I think you are expected to reload, at least in the current version of EA.

Thanks again for the feedback! Posts like these, discussing the entirety of someone's playthrough, should be very helpful for Larian to improve the game.