Seeing Carrot now, she's fighting Peros with Sulong with Sulong Wanda... So during a non-full moon and without Wanda, Carrot can't compete against vets... She'll just ending up being Chopper, Nami, Usopp tier (so-called Weakling Trio)... There's a reason why Chopper, despite probably being able to match base Robin, Franky and Brook using Monster Point, is included in that tier... Same thing will happen with Carrot and the crew doesn't need another weakling given the level of competition at this point onwards...
Imagine her joining and then BBP attacks Sunny:
Carrot: I can see rafts. (No idea)
Usopp: Eh? Wait let me see, I feel uneasy.
Luffy, ZSJ, Yamato: Feels danger.
Usopp: It's Blackbeard! We're doomed!
Luffy: Everyone, prepare for battle!
Nami and Chopper: (Cries)
Carrot: What? (Many vets and YCs already on board and ready to destroy Sunny and she failed to notice because she's busy talking to Luffy)
Luffy: Oh no, I forgot we have a new member who can't fight well against these guys without Wanda and a full moon!
Robin: We now have Weakling Quartet. Nami and Usopp can't fight against these guys as well without Tama. Chopper has no disease to fight as well.
Chopper, Nami, Usopp: Eh?
BB: Zehahahaha!
Luffy: Wait, it's not yet full moon and Wanda is not with us. Carrot can't fight your vets yet.
BBP:
Luffy:
Look, I have no problems if Carrot and Caribou joins as well IF and ONLY IF they can show topnotch power, Haki, and skills with respect with the profession they're going to fill in, 3 of the most essential characteristics of those who will join the crew at this point... I'm not seeing those characteristics with those 2 at the moment...