I suspect that might be part of why Morrison looked on in hindsight and said that he wished he'd treated each issue largely like a one-shot story. That cartoon/folktale, perpetual story quality that a superhero one-shot employs would've likely alleviated and sense of finality. I personally don't think the ending felt so close-ended, but I can see why someone might feel that. I recall Morrison likening monthly comics to something of a live performance or improvisation.
"Mark my words! This drill will open a hole in the universe. And that hole will become a path for those that follow after us. The dreams of those who have fallen. The hopes of those who will follow. Those two sets of dreams weave together into a double helix, drilling a path towards tomorrow. THAT's Tengen Toppa! THAT'S Gurren Lagann! MY DRILL IS THE DRILL THAT CREATES THE HEAVENS!" - The Digger
We walk on the path to Secher Nbiw. Though hard fought, we walk the Golden Path.
That's a good comparison. It's kinda what I mean in the sense that Morrison was like an Oscar winner stuck in an improv role. Batman was sort of improv, but more like one where the audience didn't shout unreasonable demands. You can lose him for months in a simple mystery and build to the point that the world is so much bigger and more challenging than he knows. Superman meanwhile conquers ideas thrown at him and it's apparently tough to adjust for scale. Morrison might wish he added more in, but I'm not surprised that he hasn't gone back and doesn't seem to plan on it. Superman consumes ideas. He's "said his piece."
Which is why I think I may revisit Lobdell, if not just give him more praise for his less lengthy stories. Guy wrote half of everything in the 90s, he's a reliable idea factory. I'm definitely revisiting Doomed in November.