Fans were super disappointed by the Tom Welling cameo in the Crisis On Infinite Earths Arrowverse crossover which saw it learned Clark had given up his powers, and his Superman was never shown.
The real reason Tom Welling didn't appear as Superman in Crisis is that the actor didn't want to - and never does want to - appear on the screen as the Man of Steel, but executive producer Marc Guggenheim, at least, explains they did come up with the idea to tie things into the Christopher Reeve Superman II movie where Clark gives up his powers to be with Lois (via Fake Nerd Podcast):
We discussed a nod to, believe it or not, Superman II. It wasn't relevant to the story that we were telling in terms of getting into the specifics of it, and there are certain things that I believe are best left for the fans to discuss and debate.
I don't believe in giving the fans the entire picture all the time. But the idea that Clark would give up his powers in order to have this kind of life, that really resonated with all of us, and I think it really resonated with Tom [Welling]. It just makes sense.
It was one of the reasons why it was so important for us to show you those Daily Planet articles that Lois wrote. We very much wanted to tell the audience that the promise of Smallville was, 'He's going to become Superman.' We wanted to make it very clear that that did happen, that he did become Superman, that he did have all these adventures, but they are left to your imagination.
Crisis: Tom Welling is no Superman
While the Christopher Reeve Superman actually realized that the world is better with Superman and ended up getting his powers back, the Tom Welling version failed not only the universe but the multiverse, as the Smallville Clark Kent went about things as normal and saw his Earth - and family - destroyed. Not real super.
I would have rather had no cameo from Tom Welling than what we got in Crisis, to be honest.
Guggenheim even previously revealed that Welling loved the idea of no powers for Crisis.
"He was like, ‘I love this,'” said Guggenheim. “He basically said to me, ‘You guys have basically written the one scene that I can’t say no to,’ which was really really nice.”