That was true in the past and is still true of many budget friendlier bikes that would never see Transmission, but no, generally the rear derailleur is the failure point on most high end bikes/drivetrains now. Or the derailleur and the hanger in a really bad event.
Since 11-spd came out, and then much more so with the advent of 12-spd bikes have needed to be a lot more precise for cable shifting to work well (which is part of the impetus for AXS to begin with). Cables and housing need to be in better condition and hangers need to be straighter and much stiffer.
Put another way, if you bolt any 12-speed derailleur to an old frame or basic hardtail with a classic replaceable hanger you’ll be trying to tune your shifting constantly.
Classic hanger. Bends easily to save drivetrain and frame.
Modern hanger is very stiff for optimum shifting with the precision required by 12-speed drivetrains. Usually out survives rear derailleurs.
March 25, 2023, 7:40 a.m. - Andrew Major
That was true in the past and is still true of many budget friendlier bikes that would never see Transmission, but no, generally the rear derailleur is the failure point on most high end bikes/drivetrains now. Or the derailleur and the hanger in a really bad event. Since 11-spd came out, and then much more so with the advent of 12-spd bikes have needed to be a lot more precise for cable shifting to work well (which is part of the impetus for AXS to begin with). Cables and housing need to be in better condition and hangers need to be straighter and much stiffer. Put another way, if you bolt any 12-speed derailleur to an old frame or basic hardtail with a classic replaceable hanger you’ll be trying to tune your shifting constantly.  Classic hanger. Bends easily to save drivetrain and frame.  Modern hanger is very stiff for optimum shifting with the precision required by 12-speed drivetrains. Usually out survives rear derailleurs.