Will you be still making a fuss over it?
Maybe the developer intends to some day change the internal implementation, such that that particular boolean flag wouldn't make sense any more. Or they're considering taking out the option entirely, and thus simplifying the codebase by making it so it only works one way.
Maybe the developer just doesn't care about your use case. If I have a project that works fine for what I do with it, why should I also care about some other use case you have for my work? I'm not your employee. Your product doesn't put a roof over my head.
I don't want a job where I do free work, for a bunch of companies who all make money off my work. That's a bad deal. Its a bad deal even if my code gets better as a result. I have 150 projects on github. I don't want to be punished if any of those projects become popular.
We can't go around punishing projects like ffmpeg or ruby on rails for the crime of being useful.
The pattern I have seen is that if you want to contribute a fix into a project, you are expected to "engage with the community", wear their badge, invest into the whole thing. I don't want to be in your community, I want to fix a bug in a thing I'm using and go on with my life.
Given the usual dynamics of online communities which are getting somehow increasingly more prone to dramas, toxicity, tribalism, and polarization, I just as increasingly want to have no part in them most of the time.
I think many projects would be better for having a lane for drive-by contributors who could work on fixing bugs that prevent their day-to-day from working without expectations of becoming full-time engaged. The project could set an expectation that "we will rewrite your patch as we see fit so we could integrate and maintain it, if we need/want to". I wouldn't care as long as the problem is taken care of in some way.
You could also just pay for it.
Most open source projects have way more patches contributed than the core developers can handle, so they tend to only accept those from the friendliest contributors or with the highest code/documentation quality.
Some simple setting expose like you describe can sometimes go in without a fuss or it can stall, that depends on a lot of factors. Like the other reply states: it could go against future plans. Or it could be difficult for the maintainer to see the ramifications of a simple looking change. It sucks that it is that way (I have sent in a few patches for obscure CUPS bugs which have stayed in limbo, so I know the feeling ;-) ) but it is hardly surprising. From a project's point of view drive-by patches very often cost more than they add so to get something included you often need to do a very thorough writeup as for why something is a good idea.
> I just as increasingly want to have no part in them most of the time. If all people you meet are assholes.... ;-P Not to say you are an asshole, or at least not more than most people, but I have been in this situation myself more than once, and it really pays to stay (overly) polite and not let your annoyance about being brushed off slip through the mask. The text-only nature of these kind of communications are very sensitive to misinterpretations and annoyances.
It would be nice if all you'd need for a patch to be included somewhere was for it to be useful. But alas there's a certain amount of social engineering needed as well. And imho this has always been the case. If you feel it gets increasingly hostile that's probably your own developer burnout speaking (by do I know that one :-P )
Then say you don't expect contributions at all. That's a fair game, I'm ok with it. I will then exercise my rights granted by your license in another way (forking and making my own fix most likely). My gripe is with projects that write prominently "PRs welcome", and then make enough red tape to signal that nah, not really.