I’ve been in a relationship with a guy for 6 months now.
Not at all. Partying with his friends is more important to him than spending time with you. Now you have to decide if that is acceptable to you. It wouldn't be to me.
Everyone is allowed their own comfort zone in a relationship. You have certain parameters and expectations of how you would like your partner to be. Your current partner is not fulfilling these epectations as far as the things you have described here such as spending time with you versus his ski friends,
It sounds like you have entirely different lifestyles. Skiing (and partying) is obviously a very big part of his life and if you're not that into it, you were never going to be compatible. Being regularly late to his plans with you and spending more time with his friends than he does with you was just a result of the fact that you have such different lifestyles and interests. His friends are obviously hardcore skiers as well so it's natural that he wants to spend his time with people who share his passion. It sounds like you gave it a go but you're just not as passionate about it as he is and so it was never going to work out. You definitely did the right thing by ending it.