With the idea that "quality" in this context means something that brings value to the community in the form of education, entertainment, artistic-value, scientific-value, or engagement, plenty of people have time to write more.

Is Steem just a forum for the best and most original content related to crypto-currency and blockchain? Is it even just for the most well thought out topics by experts and masters of any given subject?

I don't believe so. I think the most value that can be brought to the Steem community is to make it accessible and valuable to the widest possible audience, and therefore to post content that is engaging and valuable (in one of the ways above) so that we create a diverse and amazing platform for discussion.