David hinted at this (and I agree with his assessment that no we are not too quick to close these days) but I think it bears emphasising that up/down voting on posts should not correlate to close/open voting. These are two completely separate functions for a reason and the use cases for each are different. Somebody could put a ton of effort into a very good question and have it be off topic for this site. It may even be a question that interests some people here and in another venue they would love to engage. Being a well researched or interesting question doesn't change whether a subject matter or scope is appropriate for this venue.
On the other hand a post could be waste-bin quality writing, hastily put together or even borderline trolling and yet still be on topic, clearly scoped and answerable given this site's expertise.
In other words, it's quite valid to upvote a post and vote to close it at the same time, or downvote and specifically leave it open. The considerations that factor into those voting mechanisms are just different.
Also remember that the up/down voting privilege kicks in really early while open/close voting comes at a much higher rep threshold. This is because it's really easy for people to understand what posts they like or don't like, they personally consider useful or not useful, etc. It's a bit harder to get your head around the scope of the site and the ins and outs of the Q&A format and make good choices that reflect this as to open and closing questions. We hope that people sticking it out for a little while and learning how to make decent posts themselves learn to recognize when a post is not right for the site even when it's well composed and interesting in its own right.