A couple generations of composers decided tonality was "exhausted" and tried new resources.
A new generation, a little later, decided they didn't want to be bossed around and had their own ideas that did, in fact, involve tonal centers, in fact often included very simple / diatonic harmonies.
A little later again, we still have both types, and periodically they like to argue that the other side is deluded and wasting their time.
The question, perhaps, becomes not which side is correct, but why we feel compelled to bicker about it at all.
It seems to me that we probably no longer have sides at all, but rather a kind of enormous sphere of individual musicians connected by various landmasses and tributaries through time and geography and style. Periodically one of them discovers a group or -ism or blogger or contest or commission or ensemble or record label that makes them feel justified in this crazy pursuit and/or gives them some money. Their position becomes more secure. They discharge intellectual weapons at people/groups of opposing positions in order to cement this new foundation.
And then, generally, things shift, the rivers flood, the continents drift and crunch together and whoops suddenly there's a new mountain range there. And new theoretical resources are required to pin down the new situation for everyone.
That's my suggestion, anyway: that it's mostly about personal justification and security and $ $ $ $ $. Matthew Guerrieri has some other ideas in a terrific, non-polemical article on this usually ponderous and irritating subject.