They/Them is a dissatisfying slasher that has interesting ideas, and a decent first half. But quickly divulges into a dull and uninspired slasher.
Starting off with the good, Kevin Bacon and Theo Germaine are very good with the material their given. Theo Germaine especially is a standout as this actor gives some surprising depth to their character. Speaking of depth all of these young kids actually have some character scenes that feel real. There's quite a bit of great emotional scenes between these characters which really made the film more grounded. And the first half of this film was actually somewhat decent. The physiological horror is actually done pretty well.
However despite some good ideas and good character moments, this film is a tonal mess from the last 30 minutes. The pacing is way too slow, in fact it's not really even a slasher for about 75 minutes. The movie builds to really nothing. It almost makes the slasher part of the film feel unnecessary, and almost a completely different film than the first half. The kills are very dull and uninventive, there's no creativity here. There's no tension or even any chase scenes. The movie falls back on a lot of horror clichés, and it made the final act very boring and disappointing. There's also some really bad editing in the final 20 minutes that make some scenes involving a certain character and the killer make no sense. And finally the killer was blatantly obvious. It's a terrible twist that you can see coming a mile away and really it makes you look back and see that none of our protagonist were in actual danger with the killer
Overall They/Them has an interesting premise, but doesn't do anything with that premise and offers no thrills, no blood, awful motivation, and a lack of scares.