Simply not true. It's thriving. That's why the prices keep going up. It might go pop but no real signs of it yet.
Attendances are much higher now than in the 80's. Clubs are building bigger stadia because in the top 2 leagues they're often full. Some clubs have a 25 year waiting list for season tickets.
There's a been a drop off in attendances this year in the premier league but Luton and Burnley have been relegated so that will go up next.
This site is well worth a look if you like statistics.
Total attendances England by Division. Includes Non-League.
https://european-football-statistics.co.uk/index1.htm
Rotherham United
https://european-football-statistics...eague/rotu.htm
Not the only lower league club who has a new/ish stadium that brings in more supporters than 40 years ago.
Attendances have fallen for the FA Cup but that will be due to replays being more or less done with and because it has lost it's magic due to greed and the power the premier league have.