Some reasons to continue using firefox:
1. Containers! This is one of the biggest reasons to stick with Firefox. Along with the multi-account containers extension, you can restrict opening of specific domains to specific containers. Gives a huge privacy boost.
2. uBlock (origin)
3. uMatrix
Never used uMatrix but looks like it's a content blocker like uBO. any reason for using both instead of just uBO?
My understanding is that uMatrix is a bit different. By default, it will block just about all third-party requests. It can sometimes be a pain to manage, in particular for sites with many redirects and an absurd number of domains. I'm thinking Azure/Office365.
It's not a full replacement for uBO either because it won't attempt to do anything fancy to block ads specifically.
However, uMatrix is no longer maintained. Its GitHub page [0] says the project has been archived. I'm still using it, don't know whether there are any risks in doing so.