I think in some aspect fan fiction can keep the IP’s popularity during the official works ‘Vacuum period’,but the problem is,they showed up and speard out too much,they are everywhere,and they just effect normal audience
For example,once a time I search a ‘Ironman vs Captain America fight scene’ on Youtube,and I saw comment are all about ‘Wow Husband beating Wife’
’Tony and Cap should be the couple’
’No bucky is Cap’s wife’blablabla…comment,make me feel so weird