As another 27 year old programmer, I 100% agree. The only real benefit I think I derived from working at a company (both large and small) is getting a good idea

As another 27 year old programmer, I 100% agree. The only real benefit I think I derived from working at a company (both large and small) is getting a good idea of what works and what doesn't work for large scale projects (which I wasn't exposed to in school). And even that lesson was learned pretty quickly, within 3-6 months. All returns were diminishing exponentially from that point on. That same lesson could be learned in the same time frame in a start up - you'd just end up with some throw away code after a pretty short period of time, which isn't a big deal at all when it comes down to it.