This.. I so much agree with this.Superman is interesting because way, way early in his history he was already going like ... all the places. Stopping urban local crime in Metropolis, stopping Nazis in Europe, going to space to stop space tyrants, ultimately going extra-dimensional or higher-dimensional to stop alt-universe menaces and higher-dimensional abstract threats.
There's certainly no "area limit" on the notion of one guy who dislikes bullies and tyrants and how expansive the scope of those ideals can get. But obviously if you're having Superman go multiversal every issue you don't have much time to flesh out or develop his supporting cast who are mostly native to Metropolis. And while 'multiverse threats' are sort of 'everyday' for Superman, when stuff like the multiverse or higher power fifth-dimensional beings or even space tyrants come to town, it should definitely merit more "story" beats than just an alien lands and a slug-fest ensues.
Alien invasions start with X-Files conspiracies perfect for a crusading journalist. Multiversal infringement has all those great Fringe type things that can happen. God-beings touching down on earth to fight god-wars need some serious lead-up time (like Kirby's build-up to the Super-War).