I think they're stuck in a vicious circle, their server costs scale with size but new users are way more likely to donate. Users that have already donated feel like they've done their bit for a while, and that's if they're still around and engaged in a few weeks. Very few people want to donate monthly, subscription style.

My personal controversial view is people should put more faith in well-run self-hosted instances. It's a much more sustainable way to run a Fediverse server and self-hosted doesn't have to mean amateur hour. Just because an instance is cloud hosted doesn't mean it's well configured or secure either.

I have way more resources at my disposal than the vast majority of cloud hosted instances, for a tiny fraction of the cost. lemm.ee for example is very well run but has to put up with a 100kb image size limit because of cost-driven space constrains.

Self hosting is also closer to the spirit of what decentralization is supposed to mean - your server ultimately belongs to your host.