Well, I agree that people complain more often than they post a thread saying, "I love how things are!" But I have noticed the complete absence of any threads extolling the virtues of using CRs to build appropriate level-appropriate encounters, and using them to do so, whereas there have been innumerable threads (look them up!) that talk about how they are busted, don't work, are problematic because the MM was released before the DMG, etc.
And for those of us (like you and me) who don't care, it's because we ignore them in whole or in part and don't really apply them, instead looking at the monster holistically. And, in addition, we state that really matters is how the monster is played, the context, what the monster is paired with (solo, in groups, what kind of groups) and so on.
So I'm not sure what we are arguing about?
Ha, well, to jump on this agreeing/disagreeing chain, I'll extoll the virtues of CRs for how I use them in my game.
I don't plan "level-appropriate" encounters, but I do scan lists of monsters and CRs while populating a dungeon. I'll throw in a few monsters of higher CR, several of equivalent CR, and a bunch of much lower CR. This works even better for wandering monster tables, though I widen the CR range a bit, and use the CR to eyeball how many will be encountered. (Rolled randomly, but it's a difference between 4d6 kobold refugees and 1 Wyvern.) The DMG includes "monster by terrain" lists that are very helpful for this. Players are encouraged to choose their fights wisely.
For combats that I
know PCs will fight, either because they are almost unavoidable, or because there's no way players won't take the bait, I use an encounter calculator (that does all those damn modifiers for me) to help turn down the number of monsters. Nothing grinds gameplay to a halt faster than an overly difficult combat, especially early on.
At higher levels, as characters become more specialized and start to develop outrageous strengths (while keeping their achilles heels), I have to work a little harder and actually comb through the Monster Manual looking for monsters with traits that will target those weaknesses, and make sure to put some of them in the dungeon. CR doesn't help too much here.
For final fights or boss fights, the condition that characters are in when they arrive is at least as important as the actual difficulty of the encounter, no matter how you choose to calculate it. Are they close to full health? Do they have high level spell slots left and other abilities? Were they able to take a short rest before reaching the Big Fight, or did they use a lot of their short rest abilities in the penultimate encounter? CR doesn't really help here. I guess, if I were able to accurately predict the adventuring day, I could use that table as a guide, but there are too many variables in what my characters face (and when and how), for me to be able to budget that stuff out in any scientific fashion. But I can't really see much changing that, beyond either changing the way 5e resources or managed, or Wizards being more direct in saying, "Seriously, guys, just wing it."