Wordpress has had an activitypub plugin for years, in part because it’s an open source project.
I can see why a company with so many separate products like Meta would want to look at federation, but I’m not so sure about Tumblr. Part of their value is in having a walled garden so you need to join them and see advertising from them.
There’s a button in settings to not show bot accounts. I clicked it when I realized how many posts were just reddit mirror bots