I don't intend to try to convince you to stay. That's your personal choice and I'm not going to tell you whether or not spending time on this site is is a wise use of your time because I am not you and there is no way I can know what is best for you.
I will say, however, that we value every member of this site though and you have made many high quality contributions, and we would be sad to see you leave.
That being said, I'd like to address some of your points which will hopefully help you make your decision:
Separate fact from opinion in your answers
Let's start with the example you state inspired this question. In a recent answer you said:
First, the imp isn't technically under the player's control -- it's an NPC supplied by the Warlock's patron, and works to further the patron's goals
Commentors requested that you provide a source for the bolded section because the way you phrased the statement implies that it is a fact (when in actual fact, the books don't say this; they do say that the familiar "always obeys your commands" though which largely contradicts your point). This is not a matter of rules citation, but of factual accuracy. As pointed out in a comment:
While the second point is an interesting plot idea it is absolutely not reflective of the feature as written, please clearly separate between what's actually in the rules and what are your own ideas to flavour things up.
If I said as a thesis to one of my answers, "a dragons' diet consists solely of garden gnomes in 5e Forgotten Realms" it is right for people to call me out on that. It is possible that in my games dragons only eat garden gnomes, but nothing in the texts give the basis for claiming this is a fact for everyone reading my answer.
We want people who can bring useful experience to their answers
An easy correction for your answer that would likely have assuaged at least some of the criticism would have been to edit your answer to say:
First, the imp isn't technically under the player's control -- it's an NPC supplied by the Warlock's patron, and as a DM it is entirely reasonable based on [support] to rule that it works to further the patron's goals [and here's how it worked out when I tried it].
This is much improved because it distinguishes what is factual and what are things you are bringing to the table. And we want people to bring personal stuff to their answers, but we need them to be clear about it and properly integrate it into their answer.
So, to sum up, this isn't an example of "rules lawyering" this is a matter of voters rewarding accuracy in answers which is something that we expect and need voters to do. If you say something is a universal fact, you need to have something to back it up. Or, if it is not a universal fact at all, make sure that is clear.
If you can't cite the rules, don't answer questions that require rules citation
I can't cite rules in my answer (short of memorizing the entire library, at least for the current 5e D&D) because I usually read and answer from work, and my employer's network blocks all access to gaming related sites
You've been told this before: but answers on this site must be backed up. This doesn't have to be with rules if the question is not about rules, but good answers must include some sort of support. This is core to the entire SE system not just RPG.se.
If you don't have access to the rules to sufficiently back up a rules answer, then your best option is to wait to answer these questions until you do have access or just don't answer them at all. That is what I and others do to get around this issue.
You say yourself that you have not memorized the rules, and, in fact, in previous answers you've stated things in your answer that are factually incorrect (potentially even including your statement about familiars) and had you had access to the rules and looked it up would have avoided a mistake.
The fact is though, a single person's access to rules during a certain time is not a compelling argument to change or ignore site guidelines for a worldwide community that operates around the clock.
it's become almost impossible to ask any question related to reasonable play of the games that interest me without it being a duplicate
Well if those things are incorrectly being marked as duplicate then that would be an issue and please point that out.
Assuming that these are correctly being marked though, this is how the site is intended to work. We've all been disappointed when we had a question we thought of only to have it closed as a dupe, but the reason we do it is so that we don't spend time and energy answering the same questions over and over again. Instead we can have one place where we put all of our answers and (theoretically) keep them high quality and up-to-date so that it remains useful for any people with that same question. And, as the site gets older, we expect to have covered many questions already especially since some types of interpersonal issues just never really change and are a common issue across groups, systems, and time.
What's the point?
so why should I treat RPG.SE as anything other than a reference site in the future? What's the point?
Like I said at the top, that's up to you. Feel free to continue to contribute or not, use it as a reference or not.
If you strongly believe that answers should not require support and that answers that state ambiguous facts should not be clear where they come from, then maybe this isn't the best place for you. However, you have many highly upvoted answers on this site and a very low number of deleted and/or negative scoring ones which indicates that overall the community has agreed that your contributions are valuable. I know it is easy to have the occasional friction point stick out more than the 80% of other events, but do try to consider those times as well.
Also, as always, if you see something about the site you don't like, feel free to work to gain support to change it and bring it to our attention here on Meta. We can't or won't change some things surely but we know there is always room for improvement and we do strive to do that.