In the modern game I think it is more about 20 rather than 11. I remember when managers had one sub to work with.
Today with 5 subs from 9 it open up a wholely different tactical palate. Players in certain positions can afford to give their all over 60-70 minutes - then you can refresh legs and go again. You can protect wing backs the most demanding position on the pitch. A manager can change formation and tactics completely after 60 minutes if they want.
At times our bench was weak last year and some times had to make do with a psychological sub. One that looked good on paper but maybe was fully fit and could only give you 10 minutes at a push.
I am confident we are going in the right direction. I also believe players can improve, with the right coaching, guidance and opportunity. Players need regular football to perform at their best, without being run into to ground. With football at this level fatigue is often mental as much as it is physical especially for young players.