Sailor Stars is the final season of Sailor Moon. It is composed of two story arcs. The first one, only 6 episodes, deals with resolving a new conflict arising from the aftermath of the plot of SuperS, the previous season. It does a good job of wrapping up the old conflict and introducing the main characters' new powers, especially Sailor Moon's. It reinforces the concept of loyalty and friendship between the major characters.
The second story arc introduces three new characters, male idol singers who turn into female Sailor Scout -ish magical girl warriors. Sailor Star Fighter, or Seiya, is the central character of the group, the most important one, although others get their own episodes to flesh out their characters a bit. The three are from another planet, and they sing in the hopes that their song will reach a long-lost princess from their planet they're searching for. Seiya has a crush on Usagi, and she is forced to doubt her relationship with Mamoru, because he goes away to America for school and never answers her letters. This leaves the plot open for a lot of interesting romantic tension between Usagi and Seiya.
Chibi-Usa is gone, thank God. But interestingly, in her place comes along a smaller little girl they call Chibi-Chibi, who is very mysterious and tends to parrot what other people say rather than seeming capable of speaking by herself yet. And oddly enough, Usagi's mom is happy to take this newcomer in without even a shrug, much like she did for Chibi-Usa.
This one starts out light-hearted, like the other arcs, starting with the same predictable monster-of-the-week formula. Then, again like the previous arcs, it gets darker and scarier as the conflict escalates. The Big Bad, Lady Galaxia, is another lady out to collect all the MacGuffins, which is basically the motivation for every other major villain in the show. Except she is much more powerful, and has already destroyed countless other star systems. Turns out, the Star Lights come from such a system. They escaped from Galaxia because of the power of their princess. They fled to Earth to search for her, which is why they became idol singers; their lyrics in their... only song they ever are shown singing is a secret plea to their long lost princess. There's a lot of mysteries and secrets, but I won't spoil them here. But this season definitely has its share of intriguing mysteries, as it is the first time really that forces beyond our solar system are the major players.
Review (This Part Contains Massive Spoilers!):
Your first impressions will be that this season manages to be totally bizarre and totally conventional (following what's established as normal for Sailor Moon) at the same time, in a weird contradiction. It dispenses with Chibi-Usa and Mamoru, replacing them with Chibi-Chibi and the Star Lights. The Star Lights are... weird. It's not just their transforming from boys to girls, but also their S & M -looking outfits, their weird, long ponytails, and their attack names. One has the unfortunate attack name "Star Gentle Uterus", I kid you not. They're human-looking aliens. You come to love them and care about their struggles, but they're... different.
My big gripe with this season is how they wrote Neptune and Uranus as characters. Basically, with Mamoru gone, they become super protective of Usagi, to where they act weirdly bothered every time she so much as says "hi" to Seiya, and pressure her into avoiding "suspicious" contact with him, which means even just talking to him. But um, talking to him it turns out is kind of important for the whole "saving the world" thing. I don't get it. It's none of their business anyway, even if she was fucking his brains out. They never got so personally involved in Usagi's romantic life before, so it seems weird that they start meddling now. They become such assholes in this season that if you hadn't seen how cool they were in previous seasons, they would be your least favorite characters.
They also treat the Star Lights badly because they're not from this solar system, but from another planet destroyed by Galaxia. Their xenophobia makes little sense though, when they treat them as threats due to their "outsider" status as they themselves were once treated with suspicion from the inner senshi. They're really handed the idiot ball there, there was never any reason to suspect that the Star Lights were against the Sailor Scouts or even had different agendas; both groups clearly want to fight Galaxia and save the galaxy, and the Star Lights protect and save Sailor Moon and her friends several times. So for Uranus and Neptune to be suspicious of them still in the face of overwhelming evidence to counteract that suspicion just feels really dumb and pointless.
Another flaw is that, while the final arc takes a turn that is very serious and darker, it also kind of feels like every major battle the Sailor Scouts have had before. It's also kind of a repeat of what happened in the first 6 episodes with the battle between Usagi and Queen Nehelina. While this season is weird and different on the one hand, it also is copying the same basic formula of previous seasons.
The Star Lights' origins and nature are confusing. Does their princess have a connection with Galaxia, and what connection does either of them have to Chibi-Chibi? It's explained, but not very well in my opinion, and many questions raised by the early episodes are not fully answered by the last one.
The finale was kind of weird too, and it kind of reminded me of the "congratulations, Shinji!" scene in the end of the original Evangelion anime. Except Usagi is naked (for... reasons?) and flying with big angel wings. Did she die? Is she hallucinating all this as her brain slowly gets deprived of its last bit of oxygen? It's shown as a happy ending, but it also looks so surreal that it could be interpreted as Usagi is actually dying. Yeah, just plain weird. The ending makes little sense, it's like randomly they decide "oh yeah, I forgot I could be defeated by a ray of hope", and of course that means Usagi's hope and the hope her friends had in her.
This is fun to watch, and it will leave a lasting emotional impact on the viewer, just as much as any other story arc in Sailor Moon. But it's weird, and it's not simple transphobia that made this difficult to translate culturally to American audiences, it's also that there are many word-based puns in the earlier, more light-hearted episodes.
So, overall, I would say, watch it if you're a fan of Sailor Moon already, but it's definitely not for "normies". And, if you haven't watched Sailor Moon, obviously this isn't the place to start, it's the final arc. It has many beautiful parts though, and if you're willing to look past a little weirdness to see that beauty, it's totally worth it in the end.