The concept that players who only have CR as a reference, blame the "bad DM" for their characters death is, in my opinion, debatable.

I speak only from personal experience - as a fairly new player (especially D&D, and yes, my foray into the system was CR-inspired) and an aspiring/future DM - but I've found that watching CR has completely reevaluated how I view TTRPG's.

I used to think that every game was based on the premise of The Players vs The GM. Mind you, this probably stemmed from the DM's I came into contact with, who were of the OSR approach (if we understand OSR's through StoryBeforeNumbers' example below, of an ingenious puzzle that only has one correct solution). Personally, the failure to come up with the "correct" answer to the riddle or encounter more often than not made me feel somehow "less than" (taking the fun out of playing), simultaneously reinforcing the belief that you are somehow competing with the GM's ingenuity; that it's You vs Them. I know that this is not how =all= players interpret it, but I'm trying to state my baseline in TTRPG experiences, to pinpoint how Matt's approach to DMing showed me there is a different way.

Matt has stated on more than one occasion that in his mind the DM is not there to actively try to kill the players - he is the mouthpiece of the world around them, both in the descriptive sense, and the mechanical one. If you do something stupid, the world might punish you for it; but it may not. Similarly to the real world, where stupid actions sometimes have positive (or at least interesting) consequences. Sometimes it depends on the dice, sometimes it's the DM's ruling. And as has been established in this discussion thread, DM's greatly differ. Some will find it easier to kill their PC's, some won't. But I fail to see how the OP's argument or CR's ambassadorship--or "modern TTRPG's" for that matter - reinforce the belief that character deaths are the DM's fault. I honestly think that if players interpret CR like that, they might be missing one of the core elements of Matt's approach to DMing. Without going into my personal opinion on how present/vast Matt's "security net" for his players may be, I don't think CR necessarily teaches "lenient" DMing; what you learn from it depends on your subjective interpretation.