I made tons of friends in my 20s and early 30s. Many of them moved away to other cities with time, so I have fewer friends now, but that's also partly due to being in a long term relationship, so I have less time, and I'm still friends with some of the people I became friends with in my 20s, and between work, relationship, life and those other friends there isn't much time left for anything else. That's without kids in the mix!
However none of the friends I made in my 20s were friends borne of a shared struggle. Most of them were people I met through going to social events specifically organised for people to meet each other. The city I moved to had a lot of transient worker types moving through them so there were lots of events organised by and for expats (perhaps I should call us migrants, as that's what we were). People would turn up to a bar and know nothing about anyone except that we all wanted to make friends, and maybe even hook up. Everyone arrived alone and was trying to make new friends all the time, so if you got a few friends that way, they'd also have a few friends, and everyone would start going to similar events so you'd see each other a lot, and that branched out into events organised just in our groups - mostly very simple events like "let's all meet in the park and drink and barbecue today". It was all quite straightforward and struggle-free. As people came and went I found myself going round that loop several times in my 20s, developing new groups of friends as old ones slowly dissipated.
The only slightly tough part of it was learning how to be sociable with total strangers. Most people are a bit shy and it's not really natural to make fun conversation with someone you just met and know nothing about, but it's like anything, it comes with practice.
I wouldn't describe most work as a struggle. There has to be some higher purpose than just getting through the day. Startup life can achieve that in some way, if you're a very early employee or founder as that way the hard decisions and unexpected events are shared in your group. I'm like that right now - not a founder but a senior executive at a startup firm, and I'm lucky enough to be (by coincidence) working with someone who was in the same class as me at university, someone who I had stayed friends with throughout our 20s. And yeah, building a company is tough work, it's definitely a struggle that I feel enhances our friendship, certainly we see a lot more of each other these days!