Unfortunately, people won't take you seriously unless you have something to show for, and that is open to interpretation. Is it getting published (I am published, but my friends still don't take me "profession" seriously)? Is it selling millions of books? Is it getting on a best selling list? Is it getting some kind of literary award? Who knows?
If you don't take yourself seriously, you have no reason to ask anyone else to do the same. If you do take yourself seriously, you need to not worry about what other people think. I know, it's easier said than done -- I still get bothered when my friends and family don't take me seriously... it's like, "What does it take? What more do you ask of me?" But that's just life.
But you need to take yourself seriously, and by that I mean you can't just say "Well, I don't write for money because I just love to write. It'd be nice if I get published, but it's not the most important thing." That, technically speaking, makes writing a hobby (at least according to IRS). If you want to take this seriously, then you need to treat it as a career, a business, a profession, and not just something you do. Getting published should be VERY top on your list -- right up there with "getting the words on paper." Whether it happens or not is another matter, but if you don't even try (very hard) to accomplish that, it's hard for others to take you seriously.
Yes, the question really is "Do you want it bad enough" to do anything you can to get to your goals? I hear this all the time in the acting circle -- it's the same thing. Everyone wants to be an "actor" but not a lot of people wants it bad enough to do their best and everything they can for the trade. There is always something else that is more important -- doing chores, going to friend's birthday party, etc. They think it's easy -- how hard is it to remember a few lines, and emote in front of a camera? The thing is, if they don't even think this is a serious business, no one will take them seriously.