I see what you mean, but making a game less complex doesn't always make it worse. In this case, limiting the game to only one key requires players to quickly enter a certain number of key presses rather than recognize words, which results in gameplay that is actually pretty distinct from the typing games this is based on.
Yeah I agree complex isn't always best. and in this case I did before say it was kinda fun. But I can't see this going to the point where you could be playing this on lets say a mobile device. What Im thinking is that the game because you can only tap and count then repeat for each enemy it won't be a game that keeps its players. Take for example magic touch wizard for hire, its a game like this but instead of tapping the same key. you draw out shapes corresponding with the enemies. Its not really complex but it is more complex than this. By adding the variations it makes the game more enjoyable to play over longer periods. The added depth adds to the game having more almost "surprises". What im getting at is yes it is fun but in a realistic point of view as in if it were to be a full fledged game it wouldn't last because players will get bored of it due to it being too simple. I know this is a game jam but at least in my opinion the games from a game jam should have elements of being able to be a full fledged game. and again not that its bad but I think it just isn't there yet.