There clearly isn't a contract that they have to have DnD 5e rules in pure form. Larian has already implemented videogame elements...
Traditional DnD also does not let you long rest everywhere...
Big Picture: Larian is already on board with making changes to a PvP game for PvE...
Plot elements are also locked to long rest...

Essentially, I do agree combat is a little tepid right now. But I don't think DnD 5e is the issue and I don't think adorning a cooldown based system would solve anything. The problem is realistically elsewhere.

Originally Posted by DarkRob316
How exactly would you have a cool down system in a game with turn based combat? Time is essentially frozen during the round, and each turn is like 6 seconds of real time.
TBH FFIV-FFIX, XIV all have cool down based combat. ATB is essentially cool down based (derived from speed stat).
However franchises like Hearthstone, MtG Arena, SMT/Persona, and Fire Emblem have shown traditional turn-based combat to be more immersive than cool down-based.