Your whole thread is about nitpicking the phrase "Bevy gives you a nice ECS". You are the one who asserted that "ecs specifically is just a data structure" (it isn't, by most definitions [1] [2], except yours). I supposed you were referring exclusively to a simple and basic component storage implementation (which is a data storage), where as OP was probably referring to the whole ergonomics of writing programs in it, alongside all the other features. It seems to me that you're the one who missed the point.

Then, you used this reductionism to question whether the 50MB binary is worth it. And that's ignoring the fact that there are ways to cut it if you wish, as mentioned in the reddit thread. And then there's the issue of whether it will actually matter for a full game.

[1] https://en.wikipedia.org/wiki/Entity_component_system

[2] https://github.com/SanderMertens/ecs-faq#what-is-ecs