Well done Optimistic1 for making the brave decision to go on a solos holiday. It’s a pity you’re not enjoying it and feel that others are self absorbed.
Don’t be too despondent, I guess it always takes time to get to know someone, and it can be tricky if all they do is talk about themselves. I think this is probably quite normal on first meeting, some are used to being on their own, and talk about what is familiar to them.
I would cut them some slack, and try to take a genuine interest in some of the apparently nicer ones who appeal. It’s not for life, only for a holiday, and you may meet someone you gel with. I have a best friend who I really didn’t like initially, until I got to know her better.