It's interesting to see someone who uses DOS as a gameplay reference rather than D&D, it's a refreshing change and I think a good reminder that both systems have their pros and cons.
I personally am somewhere in between. As someone who has never played tabletop D&D (big regret, I was more of a warhammer fellow) and who has played the hell out of DOS, I feel like BG3 mixes some of those mechanics in a very compelling way. There are still some balance issues to solve IMHO, but it's getting there.
Combat can definitely feel a little bit one-sided at times, especially when you know your way around the game. I'm sure the difficulty modes will fix this. Regarding your sneak attack feedback, the way it's implemented now is actually the correct D&D implementation. It activates only if 1) you have advantage, or 2) another friendly character is within 1.5m of the target and you don't have disadvantage. I find this super interesting because as a solo player, I do not like to have to depend on another character, so I am constantly looking for sources of advantage (e.g. hide), whereas when playing multi player, that opens up more interactivity with your friends ("hey dude go stand close to that goblin so I can nuke them"). I find it interesting that you say that you were hiding in between goblins in patch 4, since this is the exact behavior that I think patch 5 is trying to incentivize. Before, I didn't bother to hide since I could just position myself behind the target. No cost, full rewards. This time I have to be a little more deliberate with my positioning and movement, which makes it far more rewarding imho. It's a different style of gameplay, but you get used to it, and in the end I prefer it a lot
. Patch 4 definitely felt more "DOS-esque", since backstab is a mechanic that was copied and pasted from that game. Patch 5 is the D&D focused version. My ONLY regret is that any character can hide in combat with a bonus action, so fighters (and even spellcasters like cleric) are just busted at the moment when this should be a defining rogue characteristic. Fix that (only rogues can hide with a bonus action, other characters would need an action), and rogues will definitely have a very distinctive "feel" to their gameplay style.
Concerning puddles, I don't think they are a thing in D&D as much as they are in DOS. You'll find a lot of posts in this forum advocating against barrelmancy, which is using barrels to make everything explode like in DOS2. I don't mind either way. I noticed that surfaces were definitely less of a thing, but I don't feel like it's taking away from the game.
I agree with a lot of your feedback on camps, NPCs and companions, but I think those are also being improved (the immersion is much improved since Patch 4 with the introduction of mini camps for example).
Thanks for taking the time to post this feedback !