Why did SE decide to make the three new classes not require base classes?

[Prototype909]

If they keep going with that, every new Job will rely on the old cross-class skills from the old Classes, which will get boring really fast.

Problematically (Perhaps) this is already sort've guaranteed to be the case. For example every tank -needs- provoke, without it you can't even do tank swap mechanics in an efficient manner. So no matter what every tank has to either be able to cross class Gladiator or have an ability that does the exact same thing as provoke but with a different name.

There will always be a dependence on old abilities like this because SE wants every job to be plug in and play rather than offering a unique experience or advantage (At least, on paper), there's nothing fundamentally wrong with this as long as it's accepted that every job is going to be a Circle Shape going into a Circle Hole.