Yea, my point was related to why people so often write their own game engine (and so rarely write their own browser). Writing your own game engine for your own game looks fun and easy from the outset. And in fact, depending on your game, writing a game engine that lets you ship that one game doesn't even have to be complex.

Right but there are smaller scale browser-like things as well which have a more vibrant DIY scene like Gopher, Gemini and so on. We shouldn't take a narrow view on what a browser is if we're not going to do that for a game engine.