There seems to be a reason that more companies are not attempting to reuse rockets [1]
So considering that, SpaceX has not proved anything, yet. Because the impossible or hard part is not launching and landing rockets. Hard part is to do it..
1. With same or more reliability than using completely new rockets.
2. Launch with enough frequency to justify the reusing procedure..
So yea. A couple of launches and reuses does not prove anything. It is a start, sure. But they have not yet proved others who didn't attempt this yet..