I think that's a reasonable position to take when actually designing adventures, but when designing a setting/sandbox, it doesn't hold. I mean, big powerful things are likely to be well known (feared), at least enough to give a clue they are there, but if the 3rd level PCs head into the Swamps of Doom where the hag covey lives (and likes to dine on travellers) they are responsible for their demise, not the DM.
More to the point, I try to do the following...

I never put a Maguffin in a place where monsters of higher power reside. If the group learns they need to recover the Ancient Spear of Malamorte, its going to be a place of CR-suited monsters.

They have a fair warning as to general monsters in the area: northern mountains have giants, the underdark has mind flayers and drow, and everyone has heard the rumors of the undead inhabiting the gloomfen swamp.

No "gotcha" monsters. This is what I meant by "surprisingly high CR monster among a bunch of low-level foes" that Older D&D modules loved to occasionally do.

Zoning Rules. Here is where things get a little meta-gamey. Most of your common, low-land areas have minor nuisance foes (goblins, orcs, etc) that are challenges early, but not later on. Similarly, local crypts rarely hold undead more powerful than ghouls or shadows, etc. You have to go to remote areas for powerful monsters to appear (hill giants don't live near hamlets, elder dragons don't build dens near inhabited city-states, and liches want more privacy than the local cemetery). When higher-level adventures happen, its because the adventurers went to the remote locales where they live or the monsters came down to visit the civilized lands (such as a githyanki incursion).

Try to pace rumors and adventure hooks to match the appropriate level. No Rings of Ultimate Power at level one quests.

When all else fails, give the PCs a bit of meta-info. It never hurts to occasionally explain that Hill Giants are CR X, or that The Lich Arthgard is known to have cast 8th level magic.