I’d like to see combat become more dynamic. As designed, it’s easy for martials to run up to their target and bash them, while casters stay back. And that’s the fight, until everyone is dead.
It’d be nice if characters had an incentive to move. Attacks-of-opportunity are a disincentive to move at low levels.
Yeah, the DM can add stuff to combat to make it more dynamic (timers, alternate goals, etc), but it’d be nice if those were built in to the system.