"But every indie developer I've talked to about game engine development acts like it's a dark art. That it's just impossible for mere mortals to do such a thing

"But every indie developer I've talked to about game engine development acts like it's a dark art. That it's just impossible for mere mortals to do such a thing, and if you do, then you'll never ever release a game, or you'll spend literal years on the engine. Again, I predict a couple weeks." It's a can of worms to make a game engine for multiple platforms.