Maps can be a demotivating factor, you get some good maps, you get maps that your f***ed on that doesn't suit your style, it always boils down to T1 land spam for 10 minutes straight until the first player gets a T2 gun upgrade or accidentally upgrades a mex and wins on eco... not many naval maps and the ones that are naval are usually the default maps, maybe add some maps that discourage T1 land spam early on and say focus on air or naval (COUGH COUGH profile stats of units built COUGH COUGH).
Maybe a map preference option before you enter the queue, but also have to consider that if someone has played a map before multiple times and has a set build order then it can ruin the fun of other players.