Base classes are a relic from 1.0 that really don't need to exist. Looking at SMN/SCH it is impossible to play both jobs at full effectiveness due to them sharing attributes and the 2 jobs feel a lot a like in terms of gameplay because you have all of the same abilities aside from job abilities/pets.

I for one am very happy they've decided to move away from base classes since I like different jobs to be unique and don't want them to share attributes which it seems won't be changing any time soon.

If anything I would say that attaching multiple jobs to the same base class is more "dumbed down" than anything.