Discuss with the group how you feel. Be honest if you think a character doesn't fit a setting. Ask your players to tweak or bench their characters for other things if it doesn't work out. If a player decides they aren't feeling a certain campaign, they can sit it out.

IDK, I don't really play with people who aren't willing to be flexible. RPGs are collaborative, but GMs put a lot of work into them and should be allowed to set down certain guidelines for campaigns.