It's too bad the culture of SO turned out the way it did. I was eager and happy to use it early on but was quickly disillusioned and it's my last resort to turn to if I have questions these days.
On the other hand I never actually contributed anything to the website... because it won't let me. One day I stumbled upon a question regarding some problem I had, the accepted answer had a C code snippet that contained an error. I thought I'd be a good netizen and decided to create an account to submit a correction. It turns out that it wouldn't let me make an edit that was less than 6 character long (why? It was just a one character typo). So I decided to add a comment pointing it out, hoping that somebody would be able to fix it for me. You can't comment without a certain reputation threshold.
So basically if I get it right if you have a new account you can only ask questions or answer them. Except if like me you only end up on SO from your search engine and generally end up on already-answered questions (or questions you don't know the answer to since you're looking for them) then there's nothing for you to do. I'm sure they must have done a lot of testing to end up with this system but it basically means that I'll probably never contribute anything to their website.
I think it's really more that it just ended-up like that. It is sad that everyone 'can't' contribute, but that's okay really. Not everyone should be contributing.
But I suspect you could contribute. You mention finding questions to which you don't know the answer. Surely, for some of those questions at least, you later found an answer elsewhere. When you do, go back to the question and add an answer based on what you learned.
It's also perfectly acceptable (and commendable) to just add an answer that's a little bit better than the existing answers. Hell, just combining two or more answers into a single (comprehensible) answer is a relatively easy way to contribute (and help others).
I feel like SO can't win no matter what it does. It has some limits, like requiring at least 6 characters before an edit is deemed useful to stop it from becoming a breeding ground for "grammar nazis" and other similar types. If they didn't do that, people would complain it's overrun with grammar nazis who don't focus on the actual code being posted. Damned if they do, damned if they don't.
The only ways to get reputation is to create content that gets up votes or do edits that improve the post.
Most of the community seems to be aware of the issue when prompted, but most times when I see moderation happening, it's not as friendly as one might hope... I always try to provide helpful pointers and comments for the author, if I happen to notice it in time.
Not enough votes. Not enough time. Poor filters. Too low a barrier to post a new question.
People then turn to social tools. Rudeness ensues.
An open question is what is the vision of the site... and there are probably many of them.
I've been a user on the site (and once upon a time a diamond mod) since the closed beta (userid < 500). Sure I've had my ups and downs and haven't always agreed with the way some things work. But at the end of the day I still think SO and the SE network is hugely useful for getting answers to questions on stuff I'm pottering about with.
There's two big camps, those who feel that SO is for everyone, and those who think they're creating a reference encyclopedia. The encyclopedia crowd won the war, and those of us who just wanted SO as a place anyone and everyone could go and ask a question without getting bludgeoned to death by high karma users have moved on.
This has resulted in a lot of questions going unasked and SO is gradually getting stale, and a general toxic element gaining more and more power within the community. It used to be that you had to take part in SO to understand how unhealthy it was, now that is leaking onto Google results.
"No question is silly" on SO is "All questions are silly."
Please note that I've answered a bunch of question, but only on a tag with not a lot of frequentation.
Even still, most newbie questions do get some degree of help from empathetic users in the comments.
Further if it is actually a duplicate what harm is there to leaving it open with a link to another question that has an answer? How many times have you looked at multiple SO questions and answers to piece together something that fits your very specific use case? For me it happens that way more often then not.