why cant i join my friend on minecraft bedrock edition?
Ask your friend if he has nintendo switch online as that is the only way to play cross platform on the nintendo switch
If your friend has Nintendo Switch Online, one of you should host the game and join through an IP adress. Be wary, not every network allows that. The only way to easily join the other player through Xbox is if they're hosting a Realm.
If your friend doesn't have Nintendo Switch Online he can't play online games. Unfortunately it's paid.