The game is complex for a vanilla player, there are some mechanics like the weak spots on tanks, uncrushable units and a sandbox more massive than the 5-6 tanks in vanilla, needless to say, there were regular Interim Apex players but to reasons like the game balacing or "bad" decisions from the developers they just stopped playing and came back to the vanilla servers.
Sometimes in Interim Apex there are 20-30 players and when game nights events the player count rise to 40 and even more, but IA is the most played of the mods and with a stable playerbase