True from a purist perspective but they've been increasing the # of games.
The biggest issue would be players getting away with more fouls so you counter that by having the subs inherit all the cards and warnings of the dudes they're replacing.
The pros of 9 subs in a 3 subs window is that it would:
1/ help prevent overuse injuries
2/ accelerate the tempo of the game
3/ allow more game time for younger players down the roster list
4/ allow more on the fly tactical adaptations by savvy gaffers
5/ I'm sure there's more ✅
The main neg is that big teams would dominate even more so to counter that, introduce hockey style subs between minutes 50 and 75 where goon enforcers get to wreck the Mobutus of the game
Also a 3min dance off at the 30th minute, winner gets a penalty but must take it blindfolded!
Fiorentino should hire me as a consiglieri 😏