5 subs is stupid. 3 subs were far better. Now, you can replace half the outfield players, which basically means you can change tactics completely. It means more of the result is down to the manager. It also means there’s less need to prioritise which games are important, you can start with your best 11 every game, and just substitute later if the result allows it. It also benefits clubs with bigger budgets more, as they can afford having a higher quality bench.
My main issue with 5 subs is that it massively favours the rich clubs. They can now bring on 5 international players. And because more of their squad can play, they can fill their squad with more top players as there is more game time