Gonna speak on this as someone who has played most of the lower tiers on here.
UU should absolutely stay, I think most things that were problematic for the tier (Celebi, Raikou etc) being gone makes it a balanced tier and a fun tier as well that allows for some variety. Of course as someone who's tried to work towards improving the tier I am naturally a bit biased. It was also the most played tier out of all the tiers during bdsp sendoff tour so it also has that going for it.
PU deserves a shot since there's an actual playerbase there and if we were just going by number of signups from the 6 opens from this year's Grand Slam, PU had by far the most although this could also be because PU hasn't had an individual since kickoff and sendoff is a bit of a weird categorization. Not to mention that one month where several lower tiers got unexpected drops and stuff.
RU, had the lowest number of signups in grand slam and it was a tier that was plagued by numerous issues throughout its history whether it was the Exploud suspect, Critdra and Venomoth utterly destroying RU during alpha, etc. There was also that time when Cress and Gyara dropped and made the tier borderline unplayable and in general just felt like a crapshoot. I think RU in its current state has a shot to really shine and most of the unexpected drops it got from that same batch can help breathe new life into the tier. (IE Bronzong kinda helped alleviate the tier's issue in handling Nidoqueen defensively) The only other issue I can think of atm that could be an issue in RU is maybe Absol but its not warping the tier to the point of being unplayable. I think RU's in a much better state as I said before even if I may be a bit biased.
NU also is a fine tier and is a must in my books. I enjoy playing it and building in the tier.
This leaves Ubers and LC which are probably the ones I am most likely voting to leave out. Ubers just had their first individual and it was ok? I don't mind the tier but it did feel like a crapshoot trying to play the tier at times. I'm not super sure how much of a playerbase there is and the tier hasn't really gotten its resources up to date and what not from what I can tell.
LC kinda faces the issue that many other LC tiers have with speedtie wars and what not. Bringing Munchlax back and banning berry juice was probably the right step in the right direction. It did show a lot of interest with that said with signup numbers but I personally am not the biggest fan of LC but I digress.
Realistically, there's like 3 options that could get voted out: Ubers, LC and RU even if I really don't want to see RU get voted out as I want the tier to succeed. LC has a shot of thriving again with the work that
Lalaya and
Kodiak_45 has done with trying to fix up LC. Ubers probably has the weakest case of staying right now if you ask me.
Edit: on a side note voting out RU would also be like an awkward tier gap lmao so yeah it's probably ubers ngl.
Edit 2: Now that I've heard things from the perspective of
Kodiak_45, I am convinced LC should be given a legitimate shot to see if signup numbers could be sufficient.