Actually I can think of two examples where tumblr rolled back an atrocious change:
Tumblr Live, which persisted for like 2 years with an average user count I can only assume was in the two digit range. This was an extremely ill advised contract they signed with a third party streaming vendor and ekeing back pennies from its fifteen annual users until they could cut the money sink loose once the contract was up was kind of pathetic. Optional feature nobody asked for and nobody used.
Group chats. This was more of a half baked idea that fundamentally relied on the three tumblr users who don't just have a discord or whatever. Ultimately an optional feature nobody asked for and nobody used, but was salvaged into communities which I have no interest in (what if you had another dashboard where you could do less) but seems to be relatively popular with some people.
...unfortunately removing the core feature that tumblr is consistently praised for, continuous and freeform reblog chains, the format that allowed for the dissemination and collaboration of Goncharov, cited as a positive creation unique to this website that gave the website rare actually good press for a while, for example, is not just an optional feature people can opt out of. Disinterest in this new format unfortunately comes in the form of uh, not engaging with posts? Not reblogging from your friends? Being drowned out on your own posts by people who comment "um quick question what the frick??" on everything. Its dire. It's going to result in less posting, less trust in the platform, and less time spent on the site slash app.
They could tank the money bleed of Live, Group Chats probably cost next to nothing after the development time investment, but less posting? Thats less ads. That's less regulars buying doodads to put on their posts. This is yet another hollow attempt to replicate other (worse) platforms at the expense of site culture. Awful. @changes cut your losses now, kill the project, it is a disaster and every second spent trying to polish the turd is going to cost you down the line. I don't know if anybody is left at tumblr who intends to still be working there this time next year but a good way to do that is make sure there's still a sustainable userbase.