The real danger is in extensions that are safe to use but later get sold and updated to spy on you with the same permissions you've already granted.
Best practice, as someone else already mentioned, is to use as few as possible and only those you trust or have wide community trust to help extend your own trust.
Extensions I trust/use:
- uBlock Origin (by Raymond Hill AKA gorhill on Github)
- Snowflake (by the Tor project) doesn't require any permissions.
- SingleFile (by gildas-lormeau on Github)
- Firefox Multi-account containers (by Firefox, obviously)
- Dark Reader (by the Dark Reader Project)
- Wayback Machine (by the Internet Archive)