It's a trade off, we made it collectively.
This is also true to some extend when it's a project you started. I don't think you should e.g. be able to point to the typical liability disclaimer in free software licenses when you add features that intentionally harm your users.
No. If it's free and open source, all it says is what you can do with the code. There is no obligation towards the users whatsoever.
If you choose to depend on something, it's your problem. The professional way to do it is either to contractually make sure that the project doesn't "fuck you over" (using your words), or to make sure that you are able to fork the project if necessary.
If you base your business on the fact that someone will be working for you, for free, forever, then it's your problem.
No. Open source projects are open source projects. Open sourcing my code does not mean at all that I have to build a community.
> The obligation is
There is no obligation. Again I don't say that authors should be jerks (obviously they shouldn't), but what seems very unclear to too many people is that users are not entitled to anything at all.
Because you choose to depend on something that someone provided for free does not mean they now owe you anything. Just like if I donate 20 dollars to a charity, it doesn't mean that I must now volunteer for that charity.
Users of open source often feel entitled, open issues like they would open a support ticket for product they actually paid for, and don't hesitate to show their frustration.
Of course that's not all the users, but the maintainers only see those (the happy users are usually quiet).
I have open sourced a few libraries under a weak copyleft licence, and every single time, some "people from the community" have been putting a lot of pressure on me, e.g. claiming everywhere that the project was unmaintained/dead (it wasn't, I just was working on it in my free time on a best-effort basis) or that anything not permissive had "strings attached" and was therefore "not viable", etc.
The only times I'm not getting those is when nobody uses my project or when I don't open source it. I have been open sourcing less of my stuff, and it's a net positive: I get less stress, and anyway I wasn't getting anything from the happy, quiet users.