I think 2D graphics is also mainly a WebGL problem. Fill a vertex buffer with 2D vertices each frame, and try to render it with as few draw calls as possible (e.g. fill vertices sorted by texture, and only issue a new draw call when the texture changes, pack small textures into a bigger texture atlas etc...). Most what makes this fast is how WebGL is used and can be done quite efficiently from JS too. WASM may help in the tight loop where the vertex buffer is filled with data though.