Probably everyone higher rated has noticed that TMM is pretty dead in the 1500+ range. Part of that is certainly that it isn't new anymore and the race for the top 10 on the leaderboard has been won.
But a big part of the inactivity I would put on the map pool. I personally stopped playing it cause I didn't like 70% of the maps I was getting. I still don't like the maps I'm getting and I am the guy that curates the maps for the TMM pool atm. Most maps I don't like are for the <1000 rating bracket, which makes up more than half of the pool:
On top of that, if I queue solo I have a good chance of being matched with a <1000 player against two 1400s so everyone in this constilation is locked to the sub 1000 part of the pool. So the effective chance to get a 1500+ map as a solo 1500+ player probably 20%.
I have suggestions to fix that: First one is to pick the maps not by the rating of the lowest rated player but by the avrg. rating of all players. I expect a low rated player to be able to handle a more complicated map with the guidance of a higher rated player, or the higher rated player just grabbing a bit more of the map.
Second one is to reduce the pick probability of a map if the avrg player rating is significantly higher than the bracket of the map. (exact Probability distribution to be determined)
Let me know what you think.