So I'm working full time as software dev but I find it extremely difficult to find some time to do open source projects. There are some rare cases when I actually use some open source library at work, and encounter some bug or missing feature there and sometimes if change requested is small enough I'm able to make contribution. But this is very rare, and in my 3 years career only happened couple of times and my patches very relatively minor. How do people implement some larger features that are time consuming and require several days or months of work?
Are you contributing to OS after work? This seems difficult to me too, as I have family and friends and also need time to unwind and relax.
It's a myth that in order to be a good software engineer you have to spend every free moment coding or that you need to be an open source contributor.
It's also a myth that all or even most employers will ignore or ding you if you have no contributions.
If you want it enough for yourself and for its own sake, schedule one evening (or weekend afternoon) a week for it - just as you would schedule one evening a week for date night or for volunteer work or for anything else you care enough about. Treat it as similarly inviolable.
That goes for anything outside work you want badly enough - learning to play the flute; writing a memoir; whatever.