Looks like we have a different understanding of fun. - Endless pre buffing before every hard fight is boring, especially if you have to do it again and again. It takes longer and longer as the game progresses. - Fights where both opponents are buffed to almost perfect immunety against everything and where you need the right spell protection and spell protection removal tools to have a chance are also not very interesting. You have to read a guide or die 100 times until you find out how to defeat that lich and once you found out you just do the same thing again and again. It only helps to frustrate new players. - I like the new concentration mechanic in 5E. You have to think carefully which spell to use instead of simply using all of them. Plus concentration can be broken easy (a bit too easy in BG3). (...)
You don't need to end buff on kingmaker. In fact, you use buffs depending on the encounter. For eg, protection vs arrows against the stag lord, protection against electricity against Will'O wisps, is not as if before every trash mob encounter, you need to do something like
And the mobs should be able to cast spells like dispel, greater dispel and disjunction to remove those buffs from the player.
As for the concentration mechanic, it RUINS A LOT OF PERSISTENT spells. I see no reason to pick any other specialization on BG3 besides Evoker. Why I would ever pick a conjuration specialization if spells like cloudkill if I can lost the spell in a single round and dish far less damage than a cone of cold would deal? 5e also ruined non persistent spells. Why pick transformation if disintegrate is extremely weaker and has a usage far more limited? Necromancer for eg, can't raise high HD undead nor OHK enemies.
All spell schools on 5e got severely nerfed. But tehre are a exception. Evokation. Meteor Swarm on 5e deals 20d6 fire + 20d6 budgeoning damage AoE damage which is 140 AVR damage. Power world kill meanwhile can only OHK creatures with less than 100 hp. Why pick Power World Kill over an AoE spell which can kill far more dangerous creatures independent of their hp?
And this not mentioning that Evokers now has tools to protect their party members from team damage.
Evokation is the unique worth school on 5e and we can't even know if Larian will ruin it too or not.
As for playing martial class on WoTR due elemental resistances, see the lich spells which I posted, casters can do far more than throw fireballs there :P
Honestly, there is only thing which I think that BG3 is superior to the competition. The enemy AI. I saw so many enemies with dumb AI in games, clerics casting heal on themselves(which damages then) on NWN1 is the most iconic example.