Simply sounds like a case of a broken coffee machine to me. All the FGW HST buffets are fitted with one on the shelf behind where the stewards stand.
If the machine breaks down, then they will use hot water from the boiler in the kitchen and some instant so that some sort of service is still available, even if not up to your exacting standards in "this day and age" (those of us who remember BR buffets in the 1970s are having a good laugh at this point) though perhaps the steward might have pointed out there was a problem.
Spot on IME.
I left FGW nearly 5 years ago and they all had (HSTS and 180s anyway) some fancy overpriced coffee machine.
After all why bother flogging a coffee at 85p when you could flog one for £2?
Firstgroup have made it quite clear since they took over GW they were only in it for the money anyway.
addendum: I now see you were on about 1st class complimentary coffee.
Must admit I was on trains every day for at least a year after coffee machines were added and no one (and I mean not one person) ever made the complaint they thought they would get the same as the buffets fancy coffee for free in 1st.
You can take it from me, that I heard EVERY other complaint that could possibly be thought of many, many times however, from the seats were uncomfortable all the way to the newspaper was folded incorrectly (I sh*t you not).
That doesn't mean your complaint isn't valid but as Jimm has very clearly and succinctly explained IF it were an issue that FGW were to have a large amount of complaints about the likelihood is that complimentary hot drinks would simply be withdrawn from 1st class, if every passenger wanting a hot drink had to have it dispensed by the buffet then:
a) standard class could go whistle as all the coffee machines time would be utilised supplying umpteen drinks to first, and b) coaches G &H would go wanting also as coach F would quite easily take until the 3rd stop to supply!
FWIW I agree with your comment that FGW don't care about their staff: they are the palest of imitations to Intercity, whom most staff IME were not just happy but proud to be in the uniform of.
I know I was in any case.