How is the mobile app terrible? I've been using it for years with no issues, and it has many extensions that chrome on Android doesn't allow like adblocking.

The tabs in FF are great, for years now FF has been much better at handing huge accounts of passive tabs, and there are tons of extensions to provide any functionality you could want.

I guarantee you if you just install a few extensions that you like and use it for a week you won't even notice any more.