For most beacon-based use cases, Web Bluetooth is not yet viable. The primary Web Bluetooth spec was built with devices you pair/connect to in mind, e.g., controlling a Bluetooth-enabled drone from a web page. Users of the web site get a popup to select the device they want to pair with/connect to. So this won't work well if you have e.g. 50 beacons deployed across a venue.
There's a separate Web Bluetooth Scanning project going on that's specifically targeted for the beacon-based use cases. It's still in the very early stages though, and I don't think any web browser implements it yet: