My current experience is I'm a 800~900 rated on the global ladder(600+ games) and around 500-600 on 4v4 TMM(<20 games).
Personal de-motivators for playing matchmaker (4v4 is my go-to) is:
- relatively long queue times (biggest factor)
- while the 'expanding map pool per rank' idea is great, I think the maps chosen for lower-ranks aren't great
- the ambiguity of it being a "ranked" or "casual" lobby is in a sense off putting (I see it as ranked, and am personally a casual player, so another negative for me)
What I see might be an issue for other, in particular new players:
- in general, the matchmaker in-client looks very bad UI/UX-side (lack of flow/direction)
- presence of the rating system (that is, it being visible) might be even more off putting to those who are straight-casuals, and aren't looking for strict gameplay