I'm an avid SoT player and think it's a great game and has a great community. The game has done really well for Rare and Microsoft and I'm sure it has brought them some financial rewards, but it's still far from something along the lines of Wow, Minecraft, Fortnite, PUBG, Counter Strike, etc.
The game has been out on Steam since June 3rd. The peak numbers just on Steam for today (6/22/20) were 58k, with the all time high (last weekend) at 66k. And that is just Steam. Since Steam, Microsoft PC and XB1 gamers can all play on the same servers, the peak numbers on the weekends are probably around 100k.
And as for player engagement on Steam, Sot is a huge time sink and gamers have already logged in 13,375,955 hours on the game.