I've not used trailblazer myself but I've utilised some of the concepts or similar ones on existing projects and green field projects.

I think the answer to 1. would be hard to express without getting deep into a specific complex application and most people don't want to open source their business applications, especially not as an example of bad code. It would be awesome if someone refactored a typical problematic large Rails app in the open using these concepts. But it's a lot of work/risk just for the greater good.

2. I'd suggest that the newer devs are going to find it easier navigating a clean codebase (with architectural complexity) than a well established Rails app with a lot of the code smells and complexity that come with going The Rails Way.