There's a big difference between armchair managers giving tactical advice about what we could have done better and us quite clearly picking an understrength side though, it's a bit of a daft comparison.
It's not a like for like comparison, granted. But it's the same principle of hindsight being used. As you yourself said, we win last night and it's hailed as a good use of the squad.
I can hold my hands up if I make a howler though, and yes people are entitled to an opinion that we should have went with a stronger team, they're perfectly entitled to their opinions, and it's an understandable view to have. My point is, if we'd have done that, and still lost, a lot of the same people would be blaming the manager for something else, and pointing out exactly why we didn't win.
Managers don't seem to share the opinion of going strong though, pretty much everybody makes loads of changes for this part of this competition, and it's more about being fair to squad members who are less likely to be given their opportunities in PL games. Or it's squad management, like not starting your only senior left back who has been having fitness issues and already being asked to play in games that he probably wouldn't start in an ideal world.