And even if WebGPU is enabled, the implementation might still be broken or inefficient in various ways. For example, Firefox uses some ridiculous polling-based approach [1] to check for completion, which disqualifies the implementation for many performance-critical applications.
[1] https://bugzilla.mozilla.org/show_bug.cgi?id=1870699
And there is the issue of getting the browser to use the correct GPU in the first place, but that is a different can of worms.