I used to have to call Euston a lot for last minute bookings (would regularly get things like someone ringing saying they're on a train at Leighton Buzzard, can they have help on arrival) and never once were they any bother. I get the impression they were constantly swamped but did seem to be doing their best.We may be an outlier, but a couple of years ago I had occasion to travel from Euston twice with a passenger who was, at the time, using a wheelchair because of a broken leg, and on both occasions we found the staff at Euston most helpful, as were the Avanti staff on the train. (Though it has to be said that the Caledonian Sleeper staff were less helpful)
Some stations are genuinely bad and it's very much just a cultural issue of "not my problem". When I dealt with complaints it was the same few stations coming up repeatedly.