One of the biggest issues that is going to be harming adoption of the fediverse is the e-mail problem, and who is enabling it.

By now it's well known what happened to e-mail. Google and pals basically control it now because essentially all the normies signed up for one service, and if you don't use Google or someone they approve all emails are sent to /dev/null to stop spam. There is a risk that someone like Google could make a big instance and get normies onto it and force them into it with defederation.

On one hand the biggest company to care about the fedi is Pixiv with Pawoo (now owned by a game publisher), but on the other hand there's already a defederation problem with instances adding other instances because they were told they're bad. Which means if you join an instance like SPC or FSE, you find yourself blocked from many instances which are just cargo culting instance blocks since they're not supposed to ask questions, just block the bad people to "protect" your users. Just like a few other cults, everyone else has to defederate them too or one click of "external source" means the illusion shatters...and you find out everyone online is actually talking shit about you.

This could happen if normies sign up for Mastodon.social or instances with janny problems as they force other instances into their janny pacts, and it's why the only way forward is to decentralize the fedi more.