Actually exploiting the information leakage isn't easy; and its compounded by the secrecy surrounding cpu internals. So I think they definitely deserve some blame here. Yes, the PoC is new. But the attack surface was widely known more than a decade ago, and they chose to punt the issue onto software; a solution that was unlikely to really hold water.
From the abstract:
> Information leakage through covert channels and side channels is becoming a serious problem, especially when these are enhanced by modern processor architecture features. We show how processor architecture features such as simultaneous multithreading, control speculation and shared caches can inadvertently accelerate such covert channels or enable new covert channels and side channels.
They were cutting corners; that deserves some opprobrium - especially given their market-dominating position over this timespan.
I am not angry at Intel and in general think they do a good job, but trying to dodge blame here comes off sounding pathetic.