Tyrargo isn’t an awful map, but it’s fucking massive, and with the multi-z, it’s pretty much impossible for xenos to effectively defend when they have fifteen xenos and three t3s.
This is especially relevant because the queen cannot cluster on lower levels, so you end up with these giant open areas that cannot be built enough to defend that ALSO do not have clusters, and the hive just gets stomped. And if the xenos do manage to dig in and defend, marines can simply walk around it, because again, the map is massive, and the sewers and upper levels give a million ways to get around anything. The only hold I could really conceive of working on lowpop would be sitting at hive from roundstart, which is boring as fuck, and encourages stalemate gameplay.