I think in Larian devs mind, freedom is more important than balance, exploits becoming a way to overcome challenge.
Exploits can be fun sometimes of course. But in a game like D&D, the combat system relies heavily on well defined rules to ensure everyone around the table get their fair share of fun by allowing synergies between characters powers.
In a game which allows anyone to basically destroy enemies by throwing barrels of oil and powder, and then ignite the lot with a torch, why even bother implementing classes? Freedom of action decreases their uniqueness.
And personally, I don't know if it's great to have a mage who can literally fight with a two handed sword as efficiently as a fighter or can heal the party with as much potency as a cleric.
