Some examples would be useful, but I must say I don't really share your concern on this. I don't see many off-topic questions answered here. <br>
At the same time, I *do* see quite some questions marked off-topic incorrectly. There seems to be a tendency to close-vote on trigger words like *bug* or the current *+1 release*, while the issue in the question has nothing to do with version-specific issues or -bugs for example.

Furthermore, I consider an unjust close vote a bigger sin than incidentally answering a question that *could* be marked as off-topic. In the first case, you send someone away who could (and should) get an answer here, in the latter case, the worst thing that can happen is that a good answer is given at the wrong place.

I don't see your issue that it invites people to post the wrong type of questions here *at all*. When people post questions that really don't belong here, it is because they are not familiar with the SE sites, not because they looked through this site's variety of questions. <br>
On the contrary I would say, in general these people are not familiar with the site at all.