There are some healthy business needs forums in specific niche like ideas.woocommerce.com

There was an attempt for the software industry oppslist.com but it looks like they did not continue this project.

One could say that Quora has alot of content like "how do i solve this" or "what is the best software for this" but Quora is organised for human information retrieval not for quantifying the market size of a certain business need and linking this to the market of companies offering solutions.