And yet 5e was designed for tabletop and WotC has greenlighted the project, so not sure how you get to decide "The current mechanics don't resemble 5e implementation."
Wow really dude

? How I get to decide? Ill say it again. Height advantage, you know being 1 step higher than someone, adds advantage +5 to the person on high ground and disadvantages to the person lower. This is a lv9 spell advantage and is better than EVERY CLASS ADVANTAGE IN D&D with no downsides. This means a ranged fighter at Lv 1 has a better or similar hit advantage moving up ONE step than a level 20 ranged fighter with class bonuses at ground level. As these bonuses don't stack said lv 20 ranged fighter is just a lv 1 fighter "up one step" with more hit points.
Free disengage and backstab advantages are part of the rogue skillset, every class can do it in BG3 so a rogue is just a really a crap fighter with low HP. Add slight of hand and stealth to a ranger and the rogue class is totally cosmetic. Imposed advantage and disadvantage is gained by most of the spells, perks and skills of every class and subclass in PHB. What is the point of these class benefits and skills if you can run up a step with any class and gain these bonuses for free against all targets?
AoO or attack of opportunity for fighters is how they fight mages and archers. They run close and wait for the mage/archer to move knowing when they do they get a free attack. What is the point when said target can just jump/run disengage, run up a step and gain advantage/backstab against the fighter? Yay go fighter!
I don't decide, Larian does. If Larian fundamentally change the way every single class in game operates with respect to D&D 5e then is it D&D 5e? If every class behaves and is used differently in BG3 compaired to the D&D 5e TT would it be fair to say it doesn't resemble the D&D 5e ruleset? With all the barrels and AoE stuff added to these alien height advantage mechanics moves it further away from D&D 5e. In fact the fight mechanics are closer to DOS in its current state.
Changing the mechanics further to compensate and keep the homebrew crap will simply make a big mess. Honesly I would be happy if Larian made D&D mode and a DOS2 mode. I am not going to pretend it isn't a big deal when all the tactics, strategy, classes and game mechanics are replaced with a bloody step. Some players like cheesey king of the hill mode, all power to them. Seriously it is fun for a battle or two but becomes a big yawn when all you are doing is looking for a step or ledge to shoot off. I believe changing these mechanics will be better for everyones game experience not just those who like D&D TT.