If it is the first few 4e books vs the core books of 2024 D&D, I think you could make the argument that 4e is simpler.
Right now 2024 D&D definitely feels wonkier at the table.
But the number of options which 4e has are still way higher which is something Reynard mentions.
5.24 has like 100 feats, 4E has 3000+, 5.24 has maybe 300 spells, 4E has 9000+, even classes has 4E with 40+ (sure with all material) like 3 times as much as 5E.
5E has more wonky rules, but 4E has more material and needs a higher tactical etc. understanding so I would put the 4E complexity definitly higher.
This just shows that such a scale is in general hard to do.
I like the framing here. I was just thinking about how I like the core mechanics to be complex and/or deep, and everything else simplified (opposite of D&D).
I gotta quibble with PF2 being more complex than PF1, because I really dont think it is. PF2 is a dense game, that benefits greatly from VTT automation, but its design is rather simple. I think folks often look at the size of the content and not the execution of the system when thinking that way.
Well the design is simple, but it put SOOO much illusion of choice over it which makes it hard. You need to select soo many (often not meaningfull) things. There are so many conditions. You need to know so many keywords. And things are written soo complicated to make classes feel more diverse than they are.
Like the Fighter in PF2 literally has only an opportunity attack and +2 to attacks, but you need so many keywords to understand this and the class has some many "class features", just to do the "save progression" + defense and attack (and attack damage) progression, which are simple. Pf1 just had 1 simple table showing these things, not 10+ class features (which are also not even named the same between different classes, and sometimes even have slight changes like Fighter randomly getting +2 to initiative in the "your perception score improves" class feature).
On top of that it has mechanics which make the game more complicated. In other D20 games, you most of the times do not have to add the number from the dice roll to your modifiers, because the outcome is clear anyway, because of the +-10 crit rule in PF2 you need to calculate this pretty much always, this also means you cant just forget small modifiers, because they might matter. Also the numbers in PF2 get even higher than PF1 numbers.