I don't think that QoS's failure as a film can be (just) attributed to a forgettable villain. Most movie villains are. I mean, seriously, we can at least somewhat recall hundreds of films that we saw, how many villains do we actually remember (plus their actor names, no IMDB cheating) as credible (not necessarily "realistic"), charismatic, and truly intimidating characters? I'll venture a list of the most memorable movie villains that I care to remember,
  • Brian Cox as "Agamemnon" in "Troy"
  • Heath Ledger as "Joker"
  • Gert Fröbe as "Goldfinger"
  • Laurence Olivier as the Nazi dentist in "Marathon Man"
  • Not sure if Al Pacino as "Scarface" or as the "Godfather" counts, since they were both the protagonists
  • Christoph Waltz as "Hans Landa" in "Inglorious Basterds"
  • Rutger Hauer as replicant "Roy Beatty"
  • HAL in "2001", and that was a f'in computer
Undoubtedly you'll find a few more, but try and be hoste, no looking up on the internet before you write if down here.

Maybe the problem with QoS is that it's dying the death of a thousand papercuts. At the core it's a long chase that is fueled by the thirst for revenge. There is nothing uplifting and positive, Bond is non-stop angry - rightfully so, he just lost the love of his life for no good reason - I can't lay my finger on anything that is particularly bad that prevents me from enjoying it. But then there's films like "High Plains Drifter" which are also non-positive, non-upliftig, driven by revenge, carried by a protagonist who seeks nothing but revenge on an entire village. And I would still be willing to watch that five times more, rather than one more time QoS.