I tend to agree, if you have a rail ticket then it simply allows you to travel as per the ticket between the two stations
If you have a First Class ticket, the train has Standard, then you are entitled to a partial refund
If your service is delayed, then you are entitled to compensation
However if the service does not have WiFi then there is no compensation
I reported the lack of WiFi on a NXEC service during my ALR in 2009 and was simply given a written apology
More recently I had the same issue on a Virgin Trains service and was given an almost identical response
I have assisted other people, and the response has been typically similar with just an apology
I suspect this is due to the service being paid for in Standard and free to First Class
This has parallels to the Shop / Buffet services, where if they are not available then there is usually no compensation
It is an interesting question as to refusing to board a service as it does not have the advertised WiFi (and hence why you purchased the ticket)
However, what would happen if the next service was also similarly affected
Equally, where a service does not have a Shop / Buffet this has to be announced prior to the train arriving so that passengers can make alternative arrangements prior to boarding, a change of Advance ticket is still not normally permitted