Is Babylonjs lagging behind?

[kzhsw]

The memory usage of gltf animations is by design, babylon.js trades memory usage (and possibily performance) for flexiblity. Babylon.js have a fully featured Animation Curve Editor that can change per-frame interpolation (where in gltf it can only be per-channel).
See this rejected proposal for more detail:

Animations: storing key frames in typed arrays

Keyframes in Babylon.js are stored with array of objects. Some animations exported with millons of key frames, with the object mode, it would take more memory than stored with typed arrays, like Float32Array. Without the object per frame, it would be much harder for features like per-frame interpolation and tangent to be implemented, so this could be an optional feature for those suffers too many keyframes without these advanced features. See code in playground: TODOs