Players have to understand while adventuring out in the world, the world isn’t level 1 like they are, the world is whatever it is, and there are DEADLY creatures out there ready to pounce on you.
Heck the original commercial for D&D even quoted, “Death lurks around every corner, learn to run!”
D&D is not an MMO, where you are in your space space area of level appropriate monsters, sorry. If you want to play with fairness and balance, play a different edition.. or go ahead and revamp the older editions to reflect your style of playing. BUT that is your job to build it in, the game itself has random wondering monsters of all types ready to be used.
So when adventuring out, look for signs, listen to the warnings and carefully plan how you’ll enter that cave or that forest, because you never know what’s lurking in the darkness!