Valve's autobattler is leaving Early Access in February 2020 as the game approaches the 1.0 version. Considering the rate at which it has been shedding players, this is not a moment too soon and might event be too little too late.
Dota Underlords launched as a major success back in late June 2019 where it managed to peak at 202,254 concurrent players. However, that number has been going down steadily since the release and the players are still leaving the game, although on a much smaller scale.
This stands to change in the future as Valve announced that Dota Underlords should leave Early Access and go into full version together with Season 1 by the end of February 2020.
Considering this is a free to play game, the loss of roughly 80 per cent players is not that alarming since many people try free games and abandon them immediately if they are not to their liking. However, Dota Underlords has been shedding players constantly and it remains to be seen how far this trend will go on.
Then again, the current numbers are not disastrous. Dota Underlords has been averaging in the 30 days leading up to the writing of this article, which is plenty of matchups to be had. It's not like failed battle royale games that struggle to get 50 players together in a mode meant for 100.