I kinda agree with this in principle.
However, I have been trying to play as much as possible to not use the free disengage, and at the moment, practically speaking, it doesn't seem viable to play without it. There are too many enemies, ranged attacks have greatly reduced distance forcing you to attack from closer, combat arenas tend to be designed so you need to be close to even see enemies, and high ground advantage for attacks and defense is so strong that it further affects the balance of fights.
If disengage is a full action, you still can drink a potion or do other things. But you shouldn't be able to attack. I don't find personally there are two many enemies. With 4 characters and this disengage mechanic, it's far too easy in most battles to the point it's boring. To even it out a little, I play with only two characters in my party at the moment.
Besides, in D&D 5e, disengage takes a full action. I think Larian went too far by making it a bonus action.
