You don't need overclocking to get "acceptable" performance. Current Nvidia cards already smoke AMD on most price points. Vega 56 being pretty much only competitive mid range card AMD have. It's just nice to have an ability to apply a good 20%+ stable overclock if needed, which definitely make card relevant for just a bit longer.
Also, HBM was a very much unproven tech when it was adopted by AMD. Not functionally. That's not what I've meant. Marketing-wise it was difficult to convince consumers why it's good, or even better than GDDR5. That was the risk, and I think it will only pay off in a very long term.
