It's worth noting that the game never really died. After the "golden age" of the early 2000's the player base organized and formed voobly, which had it's own competitive scene and even game patches for the original game (a group of developers reverse engineered it and fixed stuff like pathfinding)

And I think the game is hands down played mostly by casual players. As of today there are over 40k people that have played at least a rated multiplayer match (how many more that never hit the multiplayer button?), and from those more than 75% have an ELO lower than 1200 which is on the lower end of the spectrum (best player of the world has 2500 ELO and one starts with 1000)

The game is still pretty challenging for newcomers, my 12 year old nephew loves watching me play, but whenever I offer him a chance to play he is "scared" because it looks to difficult, and says he prefers to just watch. When I was 12 (or even younger) I loved playing. Nowadays it seems games are designed intentionally to not being too difficult to play/learn