I'm unsure whether this applies to Godot, but usually game engines come with a lot of unnecessary baggage. I think UE4 at its smallest was still something like 20 MB despite you not needing almost any of it. A 2D engine or renderer like PIXI.js makes more sense in these cases.

Good point, thanks for reminding me of these :)

I haven't really benchmarked the size, but there are a few demos floating around. Not entirely sure how to measure it, but that one seems to come down to less than 10kB? https://obersprengmeister.frozenfractal.com/

Yes, exactly.

For simple games or single animations Pixi is plenty. In fact Phaser.js is built on top of Pixi.

Phaser is not using Pixi since Phaser 3

Woops thanks for pointing that out.