Interesting post.The short answer is, different people who liked 4e liked it for different reasons, and wanted to see different aspects of it evolved and different aspects revised or abandoned. That’s also why you get 4e fans who say 13th age is the spiritual successor to 4e that Pathfinder was to 3.5, and 4e fans who say “13th age is cool and all, but it is very much not a proper successor to 4e.”
Anecdotally, I’ve observed that the folks who see 13A as a worthy 4e successor tend to play it and 4e, while the folks who don’t tend to play 5e but complain the whole time about how WotC abandoned 4e’s best ideas. I happen to be in the latter group
I've read 13A but not played it. It has good features which would make sense in 4e - damage by class/build rather than gear (the minutiae of gear tracking is a legacy feature of 4e that doesn't fit well with the general tone of the game); backgrounds and skill training rolled together; fewer levels.
It lacks robust non-combat conflict resolution.
"One unique thing" I don't find to be as powerful an idea as is sometimes suggested - how many people are playing RPGs in which the PCs are not unique in various respects? I think the approach to this in Tweet's earlier game Over the Edge is more impressive.