My irritation with the Champion as built in the PHB is that there's no equivalent class for spellcasters. If you're going to provide a simplest possible fighter subclass, where's the simplest possible wizard class? Or if we want to make the wizard superspecial and not provide an entry level subclass for it, even Sorcerer and Warlock have their own complexities in 5e and don't have a subclass equivalent to the Champion.One of the biggest regrets I think I have from the next playtest was moving superiority dice to a single subclass. I get they wanted the "roll to hit" champion fighter to be the training wheels class, but I think modern audiences can handle a fighter that got dice and maneuvers as core.
(And with the addition of sidekick classes I think they addressed that objection nicely and and also made the rationale for the Champion almost disappear. Someone who wants that 'roll to hit' fighter can play a Warrior, and someone who wants a simple caster can play a Spellcaster. )