My opinion after doing a decent amount of mentoring and demo reviewing both of Demo players and whole teams from open-mid is that mentoring and demo reviewing is mostly pointless below say div2, maybe even div1. U can't demo review someone to play mge, DM, jump maps, tf2center, dmixes, eventually pugs once they have a stable skill floor. They have to do it themselves and if they do they will quickly find themselves in divs where things like thinking about the game properly even matter. They may not necessarily win their divs if their teams don't do the same, but they will stand out and move up accordingly. When I was in lower divs I mostly just had access to public resources like demos, vods, and written pieces like the demoman bible war made, which probably has only really become close to obsolete recently rather than ages ago. Outside of that I played a lot, which is always the main way to get better.
I do think there's a lot of value in playing with higher level players in settings like pugs/centers/mixes and having their wisdom rub off through osmosis. They say a thing, you ask why, they say it's a good rule of thumb because of xyz. It happened to me and I like to think I do it for others.
no beef with the idea, it's still a nice initiative and I know you also do what I described in the paragraph above. It just saves a lot of wasted effort from mentors and the people that want the mentoring if its more focused on something like that. I do think that it would be better if there were high quality and/or more updated public resources for this game.