It was better than nothing.
Believe me, I was disappointed too. Still am. I told Tia that.
I'm just looking at where he ended up, and it makes sense. Tom has always shared resistance to be Superman. He was happy to be Clark and stay Clark Kent. That was probably one of the most annoying aspects of watching Smallville.
So he got his wish, thus why he agreed to come back.
It has been confirmed now that the scene we saw was the one he couldn't say no to. Because he loved where SV's Clark ended up. With Lois, a family, and no powers so the ability to grow old together with his wife. For what it is worth, it makes sense for the reasons we mentioned above. The story is wrapped. For Smallville. He may very well be Superman again, after some major event that will make him see the need. However, for Smallville's sake, he doesn't end up as Superman. I'm fine with that.
I have no choice either, lol. And see it this way: He got Lex Luthor to retreat after seeing Clark has no powers, haha.