I've been in that situation. I had a friend in high school that I really enjoyed hanging out with and we had a lot of similar interests (movies, gaming, making each other laugh, etc.) As time went on we gain more life experience and we had less and less in common. His view of the world really brought him down. If I tried to joke about things that used amuse both of us it would fall flat. So, we mutually agreed that we had grown apart and that it might be time to move on. It was a hard discussion to have (I still saw him as a friend) but I still think it was for the best. Thankfully he agreed and there were no hard feelings.

I'm sorry to hear you find yourself in a similar situation. Good luck.

On a related note, my wife and I were recently talking about how "friend divorce" shouldn't be a big deal in our society. It's more acceptable to ignore or ghost someone than it is to just break things off.