Karlkoth is the easiest game mode to make maps for but at the same time it seems to get very little attention from map makers.
Competitive map makers maybe, but Koth_ is the most popular mode to make levels for. I think the reason why people don't wanna make Koth_ maps for competitive is
#1. There is much higher demand for 5cp_ maps
#2. It's much easier to make unique layouts for 5cp than it is for koth, there is a reason why most koth maps use the Viaduct formula, because maps that stray from it (Nucleus, Sawmill, Harvest) are usually unsuitable for competitive play, as their layouts require spawns while become easily campable, or points which are hard to retake.
#3. It takes too much experimentation to test each and every idea that a designer might have to make a new layout. And we all know that you guys don't wanna test in-dev dev texture maps.