>The one thing that really is rough for me with _both_ UE and Unity is that they're both very oriented towards teams with dedicated art people who can put out assets to use. BSP-based workflows where you can quickly greybox out levels to playtest (basically giving level designers without art sense a fighting chance) are much nicer with older engines.

That's because the value proposition with most games is in their art direction and gameplay - nobody cares how you get the polygon on the screen. I wrote my own game engine for a bit but then realized that all the work once the scaffolding was complete was in creating a fun game. Turns out that I don't really enjoy level editing and 3D modeling as much, so I stopped developing the project.