I'm thinking of ghosting all my old friends
Why do you want to ghost all of your old friends?
I feel like it's time for me to move on and make new friends.
Moving on and finding new friends is good. But if you're still friends with people, you shouldn't just ignore them. If you don't want to be their friend any more you should just tell them why.
It would take too long for me to explain my feelings to them.
You owe them an explanation as to why you don't want to spend time with them. How would you feel if your friends did that to you? You will feel better if there's some closure to your relationship.