I guess it would fall under Design, and depending on the map, under Replayability as well, but something I think got glossed over was that you shouldn’t design “samey” maps. If you have like 5 Seize maps in a row, it can get a bit iffy at some point for the player.
This “sameness” applies to map layouts and general tactics as well: for example, if several maps (again especially in a row) feature one-tile chokepoints, the player can notice this and keep clearing maps by placing their tanky units in these chokepoints. As for the tactics standpoint - this I think ties to Design -, if you can keep doing the same thing(s) and it works every single time, you need to diversify your enemies and possibly change your map layout(s). These two can tie together in the sense that certain map layouts encourage certain strategies and discourage some others.
While this certainly ties to Replayability as well, a map can feature more than one way of clearing it and still be “samey” or repetitive in nature.
Last but not least, people shouldn’t be afraid to experiment. True, it doesn’t always pan out, but people should be encouraged to take risks and get creative with their maps. One example - notorious even, depending on who you ask - is the stealth chapter in Midnight Sun. MS generally is in my experience a rather experimental hack, which I can appreciate even when some of the maps were sort of hit and miss for me.