Tumblr is still the best place to be for many people - even despite all those flaws. For many, there is no better "somewhere else" people can "just" move to.
A dying social media platform can be as good as a new one - the incentive for spammers et Al doesn’t exist and neither do many trolls (no audience) so the remaining group can be a good cross-section.
Tumblr is the place where you get followed (sometimes even messaged) by porn spam accounts regularly.
This problem is so infamous that even some ARG creators literally used the "spam bot aesthetic" (but with weirder messages) to pull people in: https://youtu.be/ZaYioM_bsb0
>why does this person still spends their time on tumblr
Because it's not all bad? Because the problems they experience are relatively minor and fixable, and that by complaining about this bug it might get fixed?
> so I think I should make it clear that when I say "I love tumblr" I mean I love the userbase, at least most of it (obviously not the cyberbullying people with death threats part), and not the staff. the staff have no idea what they're doing and are only making the site worse
This sounds wrong too. Maybe, "Foone is they"? You don't want to misnumber them, though; maybe "Foone _are_ they"? That makes them sound epic, though: Foone are legion! Changing language is hard, whether done organically or initiated intentionally and for a purpose.
Just move somewhere else.