I made a new close friend this year. We use the same gym and started saying hello when we saw each other (initiated by me as I talk to everyone in there whereas he is very much the strong, silent type).
Saying hello progressed to exchanging a few sentences before leaving which then progressed to walking out of the gym together and chatting outside. After a few weeks of this, I asked him if he' wanted to go for coffee with me (I was sick of standing outside in the freezing cold having a chat after a gym session). He said yes. We progressed to lunches, to dinners, to day trips out, to cooking dinners at home for each other and during lockdown to walking or cycling together (which is where we're back to now grr).
This all started in Jan and during this year he has become one of my closest friends. I've told him things I've never told anyone before. People at the gym who know us both are baffled yet fascinated by our friendship. I'm an extrovert, he's a real introvert. On the surface all we have in common is being members of the same gym.
So what drew us to each other, and why have we become close friends? I think it really comes down to the fact that we have very similar values and tend to think the same way, but we are also different enough to keep it interesting.
We obviously both like the gym. We live within 30 mins walk from each other (although he was very mysterious about where he lived for ages - it was like trying to get an answer from James Bond) which has really helped during lockdown as we will walk and meet halfway and then carry on our walk together.
We slowly learnt to trust each other over time. I am very open whereas he's totally closed. But he's utterly reliable (usually early and has never once let me down). We both treat each other with respect and are considerate of the other's feelings or commitments or preferences. We both enjoy good food and good coffee so that was a good starting point. Turns out we also both like walking and we love going to new places and learning new things. He's laidback and incredibly patient but can be quite demanding (he's a barrister) whereas I'm impatient and impetuous (so he says!) and don't suffer fools (I'm a banker). We just click. I like that he challenges me (always in a respectful way) whereas he likes that I'm very driven and full of energy and self-confidence. Our different strengths (and weaknesses) complement each other and it just really works. When I was very upset about something in my personal life, he walked 17km with me in the pouring rain listening to me talk and being supportive. He's become an amazing friend yet one year ago, I'd never exchanged more than a sentence with him.
Sorry OP, that was long and rambling but I wanted to share that it is possible to make new really good friends.
I've expanded my social circle a lot over the last few years and the trick is 1) make the effort! be the one to say hi, how are you etc and 2) accept offers (or make offers) even when you don't feel like it. You never know what will happen if you say yes instead of no.