Hmm I haven’t looked at PF2 yet, guess it is something to look into.

I think 4e was just trying to be a fun game where all the players had something cool to do each turn.

It also simplified combat on the DMs side. The DM could select a player level and look for monsters of the same level instead of calculating challenge ratings.
4 minions(Xlvl) can fight 1 player(Xlvl)
1 normal monster(Xlvl) can fight 1 player(Xlvl)
1 elite monster(Xlvl) can fight 2 players(Xlvl)
1 boss monster(Xlvl) can fight 4 players(Xlvl)

With the introduction to the Monster Manual on a business card, it made encounters even easier.

The changes I would make would be to simplify/reduce the d20 number and implant the bounded accessory system. This would make many powers obsolete or require changes. But this could mean that they could just squish 30 levels down to 10-15 levels.

Another thing to bring up in my ramblings is that skill proficiencies didn’t become obsolete with higher levels. For example, in 5e, the Knock spell completely opens the lock while in 4e, the Knock power allows the wizard to use their intelligence modifier for the open locks roll. This is but one example out of dozens or so skill challenges.