I think it's possible to claim an element of success even in the absence of trophies, depending on the situation.
I don't think we're there yet. Success for us would involve at least going into matches against Celtic (and probably Rangers too) expecting to win.
If we were to go toe to toe with Celtic, obtain 90 points and miss out on the title on goal difference, that would be a fair claim for success for us.
The league being over before the split, and relying on luck and Celtic not turning up to get at least a point from them is not really success, we're just the best of the unsuccessful teams.