As an open source software maintainer myself, I don't quite agree with some of the points.

I also always believed that if you ever started a project that is valuable for companies, they would support you in return

For me, I do ask for donations, of course, because life is hard and who doesn't want money? Especially when you deserve it. But I never expect anyone to make a donation. It's only when someone actually does it that I feel so much happiness. Some leave a thank you comment and stated that they cannot support me financially, and I'm also perfectly happy with that.

All I got was complaints.

I see it as feature requests and bug reports, and are another kind of contribution. Note that some of the people may seem rude, it could be because they are simply bad at English (as am I) and try their best to write a short sentence. Some may not familiar to GitHub and talk about their problems in an unrelated issue. In that case I simply try my best to understand and kindly answer them, and guide them to the right direction.

It may seem to you that open source is great because it's free to use. Truth is, it certainly is not free.

I use open source software for free, and I want to pay it back by contributing more to open source. I don't forget that my own open source projects also have a lot of other open source components in them, all for free. I don't like to force people to pay for my softwares in order to use it.

Of course, my open source projects will forever be hobby projects, I can never make them into a serious business nor work on them full-time, but I'm fine with that.