A boy who isn’t mature enough to talk to you himself about wanting to just be friends isn’t mature enough to be going out with anyone. To his credit, he knew he should slow down. Now you should too. If you like him a lot, develop the friendship. Maybe it will grow into something more and maybe not but I wouldn’t throw away a friendship because of this. Good friends are hard to find. At 15, you have plenty of time to find a boyfriend.
I wish you well.