I will jump stright into it.

Character Creation.

You generate your character's six ability scores
randomly. Roll four 6-sided dice and record the total of
the highest three dice on a piece o f scratch paper. Do
this five more times, so that you have six numbers

Note - Taken directly from the D&D 5th edition rule book.

This is VERY important to pretty much any D&D game, D&D veteran or sentient fungal growth on a first edition rule book. Having every class of character/NPC born a physical clone of another is not fun.

New Born Baby Syndrome- NBBS assumes every player class in the world has never left the womb until "mindflayers"......Kind of breaks any immersion from the "get go" in a D&D game. It is easily remedied by the DM (devs) by generating a level based on player input. It is the reason "import character" was good in BG!+2. Different levels between 1 and 4 isn't a big deal considering all players in D&D generally have different XP. The randomness of a world IS the immersion factor, you wont see 12 level 4 goblins at a house, you will see a level 8 goblin boss and 6-8 level 1-2 goblins. Just an example. Randomlevellyness - every living being is different.

5 face presets is not character customisation especially when 4 look like wierd fish mutants. I don't know how viable the ability to move the position of facial features is? Changing the "size of" said features also. Here I go again with "randomness". Most none specific NPC's look exactly like the character you were just making....because they were. Scars, makeup, skin textures, eye patches, broken nose, missing eyes.......I know people that spend more time in character customisation than playing the RPG.

Otherwise the current classes are pretty much spot on. Oh Drow is just an elf subrace.

Game world

There are wayyyyy too many barrel hazards, water barrels, booze barrels, oil barrels and powder barrels in the gameworld from DOS2 assets to make the game feel like anything but a MOD for DOS2. When the greatest weapon in the game is the environment and the new class "Barrel Mage" that requires high str/dex rogue with the ability to sneak and a box of matches...... I mean a few barrels of booze at a goblin party sure okay but beer/grog is not Highly Explosive. Even containers of random garbage explode like semtex in almost every room on the map from the second you enter the game. I would remove pretty much all of these barrels unless, like the goblin party, it is relevant to the story. Oh yeah barrels of water don't materialise in burning buildings because the building happens to be on fire for a story plot.

Arrows and other elemental consumerbles DO NOT create massive ground hazzards. Every goblin in the D&D universe does not hold specialist grenades and magic arrows that cost 100's of gold. NPC's do not strategically place themselves on the "high ground" like psychic undead creatures that never move. They eat, they partol, they fall asleep, they poop they wonder about. Time of day is very important, you will sometimes wait until night to do stuff especially Drow and Orks. Wait till they are asleep and their vison range is two feet before WHABOOM!!! Dead humies.

Height advantages do not offer HUGE accuracy/damage bonuses and HUGE disadvantages for being lower. Far targets are difficult to hit, yes being high (really high) means you can shoot further but unless you are a specialist ranged fighter or ranger there ain't no shortbow rogue goblin hitting you 3 screens away.

Buy and sell prices from vendors is ridiculous. Buying something that has a base of 100g for 250g and sell it for 25g........Not realistic. 15-30% mark up and mark down depending on charisma is. With 18 charisma an item with a base of 100g should be 115g to buy and 85g to sell. The new PS5 isn't 1500 euros. Obviously these are examples and it would depend on the vender but 2.2x-2.5x base is too high.

These are just things that stood out.