This is a bit of an "Are Y'all with the Cult?" moment. Tumblr is a niche community at this point and the people who are still there are largely unusually dedicated fans.
People don't congregate around websites. They congregate around subject matter. Tumblr is THE place to congregate around a long tail of niche subject matter.
It's not full of Tumblr loyalists. They mostly have lukewarm opinions of the iOS app. They're on the platform for the fandom, not the company.
The fact that you refer to Tumblr as a singular community shows that you should probably not comment authoritatively on the website :)
It looks like Tumblr has a lot of traffic, but isn't growing and is far behind reddit and twitter. None appear to be growing in the last several months; I don't know what that means.
https://www.similarweb.com/website/tumblr.com/?competitors=r... https://www.similarweb.com/website/tumblr.com/?competitors=t...
Tumblr is about equal to wordpress.com hosted blog traffic, interestingly. Wordpress.com is a collection of hosted blogs with very light in-network social features. https://www.similarweb.com/website/tumblr.com/?competitors=w...