That’s definitely one factor, Enlisted is 18+ after all.
There are many other concerns though, like engine limitations, lack of maps with environments fit for infantry, lack of even basic FPS/TPS mechanics (let alone stuff like shared control of vehicles, entering and leaving vehicles, manually switching seats, etc), huge balance concerns, War Thunders gameplay and game modes being tailored for vehicle vs vehicle combat rather than infantry + vehicle cooperation, etc
Seeing what some of the players currently seem to be playing WT on, yeah I think they would need to update the minimum requirements, because a lot of PCs/early consoles would absolutely explode.
I agree, the devs would actually have to redesign every map in game or spend a lot of work on a significant amount of new maps with everything new in mind.