Why are there no (good|FOSS) 3rd party (app|frontend)s being developed for Tumblr ?
Options are few far in between , forcing me to use 1st party app . As much as it sucks it's the only way i can access tumblr , The website is awful slow even with adblockers
Given all that, it's a wonder why there's hardly any 3rd party offerings compared to (twitter|reddit)
Tumblr isn't nearly as popular as it was 8 or 10 years ago
Tumblr isn't, generally speaking, a well known site for the kinds of tech focused people that would be building such applications. Tumblr has a focus more towards sharing images (even to the extent of screenshotting twitter posts rather than linking the post itself), and generally speaking (again) more tech focused people tend to prefer sites with more generic content, such as lemmy/kbin/reddit where you can have images, links, and text discussions.
Tumblr is also perfectly usable in a browser. In fact, I deleted the tumblr app and created a shortcut from fennec, and it's honestly an improvement. There's really no reason for a standalone app.
Edit: I guess OP tried this and said it's slow. Hmmm this hasn't been my experience