AITA for not inviting someone from our friend group on a trip because they’re a negative person?

My friend group wants to do an overnight trip to a nearby city (for no particular reason other than for fun). For context, our friend group is a little over a year old. Four of us get along GREAT, and this other person just isn’t a fit and I’m tired of pretending they are. They constantly talk down about themself, complains about their life and work, and it really brings down the vibe of our group. We also just don’t have that much in common with them. They’re a very nice person but any outsider could say that they don’t really fit into our friend group. To note, they are very sensitive as well which makes it more tricky, so not sure how to slowly be-rid of them without feeling like a horrible person.

EDIT: 100% open to an honest conversation! This group started as “after work happy hour get togethers” because we started as coworkers. Additionally, this person is a bit emotionally immature and hasn’t experienced a lot of the things that the other 3 of us have / can relate to.