It takes about 90 seconds to load for me, but once it does, it's buttery smooth on my M1 Pro. Unity's web story is still so bad for many reasons, but the initial load times are a huge one (~15MB of wasm for an empty scene last I checked). They were working on Project Tiny[0] to address exactly this, but they've now paused work on it indefinitely :( Someone please build tools to fix this!
[0] https://unity.com/solutions/instant-games