The important thing to remember about topics being deemed off-topic is that it's not all random. A lot of thought has gone in over the years to whittle the scopes of Stack Exchange sites down to be productive Q&A sites.
The key, as we've all heard before, is answers.
The trouble with questions looking for quick input is that they're often not answerable.
Stack Exchange thrives, in big part, on binary truths. That is, something is either right or wrong. There are definitely sites in the network that don't conform to that standard 100%, see Good Subjective, Bad Subjective, but fundamentally, the system operates with upvotes, downvotes, and accepted answers. It's hard to accept an answer and say "this is what worked best for me," when you get two equally valid, completely separate answers.
Take the following three questions as example. I'm framing this in Stack Overflow, but similar theories apply elsewhere.
- I'm running [this code] and getting a NullReferenceException on [this line]. What can I do to get past that error?
The answer here is highly quantifiable. If I give you an explanation and maybe some code, then you understand and implement that and the error goes away, that's your answer.
This is a valid question by every step, but think of how many answers there would be to this, and how long those answers will be. You could write entire blog posts about how to do this, and worse, three people could write completely valid, completely unrelated answers. There's a lot of subjectivity here, and that just doesn't work well with a Q&A format. Maybe some developers prefer doing it manually with a canvas, or even building things server-side, and others prefer use of libraries like d3. It's nothing personal against the question, it just doesn't work great here.
- I'd like to start programming, what language should I start with?
Again, a very valid question, and one which just about every programmer will be able to answer. Sure, you could write blog posts about this too, but that's really not the issue. Most people could explain their preference in six characters or fewer. The issue here is that there's really no best answer. Someone will say "learn C, you won't have anything done for you so you'll have to learn everything." Someone else will say "learn Python, it'll handle the heavy-lifting so you can focus on the important stuff." Which of those is right? It's utterly impossible to say.
I think the best place to get this kind of advice is on Chat. Rules there are much more relaxed than they have to be on the main site. You need 20 rep points to talk in chat, but even beginners can get that pretty quickly with just ten suggested edits.
That said, I'm with Nicael--if you'd like to propose a site on Area 51, all the power to you. It's quite possible that there is a sector of questions that will fit the format but are not covered by existing sites, and if that's true, I'm sure the network would benefit from the proposal.