I guess. We don't play with a lot of magic users either. Didn't make any difference in 4e that is for sure (the edition we had the most magic users).I have no doubt you can. Whether that favors some classes and types is a different argument though (and barring other rules I think it absolutely favors spellcasters).
I make the world and then let the group explores it. Now I do sometimes give clues. cues. or hints, but if it doesn't work, well... My group once went off task in a swamp and ran into an ancient black dragon (4e - level 26 solo I think) that they new nothing about, when they were level 5 +/-. So, not exactly 1st level, but pretty close.I suspect to one degree or another you do and don't even realize it. Every D&D GM I ever saw in my life did. Its just part of the basic thought process of putting things together.
I mean, let me ask a simple question: do you have a setup where first level characters are liable to run without warning into an old Red Dragon or a high level demon? If not, that's balancing encounters. Past that, everything is simply a matter of how much effort and to what degree you do so.
Now the thing I do more to accommodate our style is everything is basically weak - more game of thrones than Forgotten Realms. Magic items, magic users, and powerful magic monsters are rare.