To me the advantage rules are the smallest issue with BG3 and DnD 5e rules. Mostly because as people have pointed out many times: It's up to the GM to decide. Many many tables house rule some form of advantage rule.
I think if that was the only "issue" with the 5e rules, then we'd not take it too hard.
But the problem is all the other rules that's stacked on. Many people dislike the "home brew Goblins", again something I don't mind, but when you make Advantage easy to get AND you make the Goblins easy to hit, you made fixed the same problem twice.
The problem is that right now in EA Larian has made too many changes to 5e, to the point where it's more like a playtest version of 6e. Each change by it self isn't a huge deal, it's just too many of them.
"Cantrips shouldn't make surfaces" - um of course they should, why this hatred for Create Bonfire? This is a cantrip that Larian really should look at. I have no idea why they didn't include this spell in the game, but made "super create bonfire" to firebolt. Create Bonfire is everything Larian wants, it creates a surface, and ignites burning material.
You create a bonfire on ground that you can see within range. Until the spell ends, the magic bonfire fills a 5-foot cube. Any creature in the bonfire’s space when you cast the spell must succeed on a Dexterity saving throw or take 1d8 fire damage. A creature must also make the saving throw when it moves into the bonfire’s space for the first time on a turn or ends its turn there.
The bonfire ignites flammable objects in its area that aren’t being worn or carried.
The spell’s damage increases by 1d8 when you reach 5th level (2d8), 11th level (3d8), and 17th level (4d8).
But it has limitations:
1. It's a concentration spell.
2. It cannot ignite materials that is worn or carried.
But instead we get Trogdor the cantrip in Flamebolt, which ignites the person, ignites the surface AND does direct damage.