I don’t know what the first one is about. Is it about how the Gemini webpage displays the output?

Don’t like how they’re doing it, you can literally spin up your own for dollars per month.

Not so easy.
Mostly a liability issue.
First there’s security - make sure the server doesn’t get compromised.
Then you need to figure out how to deal with illegal content like CSAM (was already a widespread issue on Lemmy at least once, causing multiple instances to shutdown) - even on private instance due to content caching.
And legal issues such as minimum age and privacy regulations that you’d have to comply with.

3rd one is not an issue if you only use it yourself, and perhaps with a couple of friends that won’t try to sue you when they get mad.