Removing or tweaking concentration from 5e would have a profound impact on how everything works. As we see it right now with Larian's 'small' changes.
Some people might not like it, but its an integral part of the game balance of this edition and it prevents all those utterly annoying buffing/debuffing cycles that made the game incredibly complex in previous editions (or see the current Pathfinder games). But it goes beyond just casting several spells. The whole AC mechanic is based around certain max values - if you can now easily stack buffs you break the whole balance for attacks vs AC. Not to mention that many class features are balanced around these core principles.
Larian's biggest problem with the game design of BG3 is that they far too often only see the small thing that disturbs them not paying attention to what their tweaks do for the game as a whole. Their homebrew already severely shifted the balance of the game - removing concentration would make it a completely new D&D system/edition.
