Makes for very blend boring companies. Probably also explains some part of the "lack of diversity": This person is so different than anybody else we've ever hired, let's just say "They won't fit in". This is an easy loop to get stuck in, and can really hurt people from minorities or with different background.

Unfortunately, the word “diversity” isn’t usually used in that context in the corp world. Disruption is only something to talk about, they don’t want to actually do our, nor hire anyone disruptive to the current culture.

I got my current job without interacting with HR at all. Phone screen with the CTO. Phone screen with the engineering manager. In-person interview with the CTO, then the engineering manager, then the team I would be joining. In a perfect world, prospective employees (of any discipline) would have absolutely no interaction with HR prior to being given an offer, and HR would have absolutely no say in hiring.

The perfect world you're talking about has Personnel departments instead of Human Resources. Personnel departments deal with the tactics of staffing a company without the strategic planning that HR departments do. Interaction is okay. They just shouldn't be part of the decision making process.