I do think it is a problem that stems from the introduction of combat balance as a focus in 3E.
Actually, that goes all the way back to at least AD&D - the "level" entry in monsters in the FF & MM2. Both 1E/2E and B/X had the unspoken idea that HD roughly equated to level (with B/X adding "*" to account for special abilities that made them more dangerous).
3E added
tools that codified that into CR with the idea of helping gauge what would be appropriately taxing to PCs at a given level with the flawed assumption of a well-rounded party (fighter, rogue, wizard, cleric). Unfortunately, it got taken as gospel even as WotC constantly cast it aside to build encounters for their own adventures (see the Roper in
Forge of Fury as an infamous example) and even lectured against using CR as a straight jacket for encounter building. Even the infamously balanced-hungry 4E had instances where the guidelines were put aside (the Irontooth encounter in
Keep in the Shadowfell, for example). 5E continues that tradition of squarely using it as a guideline and occasionally building cinematic encounters that ignore the guidelines - only to get pushback from the community about it being "unfair" or "impossible" to beat*.
Conversely, it is somewhat interesting to look at 1E/2E random (wilderness) encounter tables and find creatures on there that wildly didn't care about the PCs level whatsoever. They did/do exist in 3E and 5E, but it appears that many DMs have been advised by the
community NOT to use random tables such as these and to build "balanced" tailored encounters based on the guidelines in the DMG.
*Personally, I'm hoping that in the new Vecna adventure, they make the final confrontation with Vecna impossible to beat by fighting him directly. Because someone
will find a way, or more likely players will be forced to put on their thinking caps and up an alternate solution to thwarting him.