This, plus after the Godot runtime, game assets itself have to be downloaded, often making use of ZIP-like archive formats that may have made sense with DLCs or physical media, but require huge downloads (like GBs) to access a single sprite when the browser DOM rendering itself is pretty much about priorizing resources as they're viewed.

Plus, WASM game runtimes need to bundle redundant 2D or 3D stacks, audio, fonts, harfbuzz, etc. yet don't expose eg. text rendering capabilities on par with those that browsers already have natively.

The whole thing is priorizing developer over user experience.