Outgrowing a friend group feels lonely before it starts feeling like room.

The gap arrives before anything shows up to fill it. You stop fitting where you used to fit, the evenings go quiet, and nothing has yet replaced the group that used to take up all of them. That stretch reads as proof you made a mistake, when it is really just the interval between leaving and arriving.

If you are in that part, let it be slow and keep yourself in rooms where people are doing something. A club, a shift, a team, anything with a regular time. New closeness is built from repeated low-stakes contact, and none of it happens quickly.