I've lost count of the number of WFH calls where "it's shit and slow" and you find that they're using WiFi and the router is in the front room and they're working in a bedroom on the 2nd floor.
"Go and sit in the front room and plug your laptop in using a cable. Is it better?"
"Yes, it's great".
"Good"
As a generalisation, WiFi = Convenience, Cable=Stability.
Also UK stated ISP speeds are to the router, IIRC, not to any devices.