Actually common criticisms frequently levelled at them in the railway press at the time were unsuitably short formations and a lack of luggage space compared to existing stock. I can't imagine where we've heard similar criticisms recently.

Though I've not seen contemporary evidence for it, if online railway forums had existed at the time of the HST's introduction then I don't doubt that the foam padded IC70 seats, with their imperfect window alignment in standard class and low backs to boot, would have come in for significant criticism compared to the sprung cushions that prevaled on existing rolling stock. "Why can't these short modern plastic trains have comfortable seats that line up with the windows?" would be the oft heard cry.
Don't forget that in their early years HSTs gained the derogatory nickname of "trams" from the enthusiast fraternity (They didn't count as real trains), and were frequently avoided like the plague unless needed for an absolutely necessary positioning move. They certainly weren't heralded as any kind of saviour by the enthusiast community.