I just realized I only have my best friend...literally
Your story is so common these days. Is there some activity that appeals to you that you could immerse yourself in? That can open doors.
20s used to be such an easy to make friends age period but society seems to have changed so much it's unrecognizable to me, watching my girl navigate this age. I did have "dry" social periods in my 20s too though. I found solace in painting and just filling my head with classic reads and enriching myself. It was still lonely but thankfully gaming wasn't so much a thing then. I think a lot of young people are going to regret how much time they waste on gaming.
If you're finding yourself with a lot of free time use it to your advantage now because it may not always be so open to pursue interests later on.
I have acqaintances. No male friends as such, lots of kids I looked after when they were young are now grown and I see them often, but tehy are more like children to me. I have some female friends, only a couploe are still close, people drift apart. I was never very good at making friends.
Sometimes, starting from scratch can be good. I was in quite a rut before I moved to a new state and restarted my social life. It sucks for a bit, but you may find yourself in the company of like-minded people, instead of the people who had just been nearby.
I have no one, sometimes the people in your environment will pull you in a direction that's not worth taking. Be discerning with your company it's better to be a hermit in many cases. Especially as athiest tends to think differently to our fellow beings, why they say we're like cats.
In reality you only ever have a couple of really good friends and even they can change. you can't even choose your family. I only talk to my mother out of any of them and thats partly because I feel obliged too. most so called friends are fake and only with you because it suits them at the time. don't worry, after giving up religion you have just realised this is all. don't get upset but realise that is the case generally. you will get more aquantances and maybe a few good friends again as your still young and you will now naturally migrate to other people with the same beliefs hence being here.
Not everyone has a bunch of friends, however you can broaden your social circle. Check Meetup.com. You my find people who share your interests that way. Take some classes. Get involved politically. I made some friends through a Humanist organization in my area that I found through Meetup.com I tend to be an introvert. I have a few friends, my kids (who are all older than you are), several coworkers who I chat with, and.... and.... and.... this group!! But for face to face contact, I got my nails done today and picked up lunch at a drive through and did some shopping. Wow, what an exciting day!