Disagree strongly re: urban fantasy and the like , though it's a broad genre so some stuff would be terrible (most UF is not "crapsack world", not sure why you're saying it is). You're not thinking it through imho. The power levels don't have to be that extreme, on paper. It would certainly do a MUCH better job 3E's really sad attempt.
It would be imho a total nuclear disaster for superheroes because classes and set abilities are a disaster for superheroes. I've played a lot of superhero games, and only ones which let you have a fairly free hand (like M&M levels of free hand) ever felt at all superhero-y. 4E, with all it's precision-tactics and pushes and pulls and so on would be a trash-fire for superheroes.
Agree re: the rest, but level-based games are a total disaster for secret agents and so on, as Spycraft repeatedly proved over several editions of failure. Not like we didn't give it a chance. We gave it too many chances by far.
You were probably using old-monster-math monsters. They didn't fix it until MM3, and you had to, IIRC, manually fix monsters from before that (which was really easy with the DDI, but not without it). They were pretty bad. New-monster-math monsters worked extremely well.
There was another issue with the official advice, which was I think that they assumed you were going to try and do attrition, but 4E didn't do attrition, so you needed to ignore that and go for the total daily budget in fewer encounters (this also helped with combat taking too long). But the actual charts were extremely reliable, in a way that they were not in 3E (where the charts were actively misleading - eyeballing was better than using them) or 5E (where they're just not very accurate).
I know that once I worked out that I needed to go with "fewer, harder" encounters, but to otherwise use the guidelines, 4E really worked very well. Unfortunately 5E works best with "more, easier" encounters. Which feels more "D&D" (for sure - up well into 2E there are lots of adventures with tons of encounters/day, often ludicrous amounts), but feels less dramatic and story-like to me.