As someone who has hosted a few Nextcloud instances for a few years: Nextcloud can be quick if you make it work. If you want to get a good feel for how it can be rent a Hetzner storage box (1TB for below 5 Euros a month).
You sadly can't just install nextcloud on your vanilla server and expect it to perform well.
Do you have any tips and tricks to share? I'm running a self-hosted instance on an old desktop PC in my basement for me and a couple family members. Performance is kinda meh, and I don't think it's due to resource constraints on the server itself. This is after following the performance recommendations in the admin console to tweak php.ini settings.
You sadly can't just install nextcloud on your vanilla server and expect it to perform well.