[GuiA]

Building your own thing is fine if you're solo. When you start having to collaborate with e.g. artists who expect their assets to render the same way they do in their editor, or a game designer who needs to edit levels in the engine, etc., then you introduce a bottleneck due to the fact that some people are working on the engine, and others on the game that depends on the engine.

[sloopy543]

I've found that making a custom engine is more amenable to teamwork, not less.

I can build a simpler level editor that I can give to a totally nontechnical person (a.k.a. my spouse), and they can go to town making levels.

They don't need to know anything about Unity/Unreal. They just need to know about my game.

My game already includes levels my friends have designed using tools I made for them.

[soylentgraham]

This is the big bottleneck, plus, for shipping jobs (say <2 month timespans), writing some of the basic stuff eats up more time than you want.

I've been doing an engine on the side (c++ underneath, javascript on top) for pc,Hololens,magic leap,Mac, android, we , pi/Linux (finally) for about 4 years now. I can churn out tools (editors, daemons that run for months, hot-reloading remote-assets, vr apps&overlays, ML tools, streaming point clouds) and demos, but it's still missing rigid body physics and a lighting engine (outside ray marching)

I still have to resort to unity or unreal to get jobs out, because there's too much to do for one person. (Although this is finally starting to change :)