Most of the teams in the PL are like us, never likely to finish top four often in danger of relegation or just always mid table. The only exception that comes to mind is Leicester.
Unless you have any stats to suggest it, I don't see any team like us losing fans in the medium or long term so why do you think we will? Of course some fans will get bored or drop out but others will replace them. That's life.
Statistically, we've gone from an 8k waiting list to having none and only a 90% renewal on top of a previous 90% renewal, leaving us with (if the number posted on another thread by Bold Seagull was accurate) c21k STHs or 2000 fewer than when the capacity first went to 30k.
Anecdotally my mate's 15 year old son is bored with football and we've not renewed his season ticket. Another mate didn't take his 9yo yesterday because he doesn't want him getting too downhearted.
Many kids will have fallen out of love with going to football during lockdown / BCD football and many families will be struggling with budget in these uncertain times. We're not exactly helping them to prioritise the Amex towards the top of things to be kept.
Anecdotally again, did you see how many empty seats there were yesterday for a Category A game on a Saturday? Shitloads. If we want to improve the atmosphere we have to fill those seats but you'll never get the statistical facts from the club because we only publish the pretendence. We have to use our eyes.