I think having areas with weaker or stronger enemies is fine. Good, even. So long as you can tell by looking at them what you’re getting into.
Dark Souls generally does this. A rotting skeleton is a low threat. A giant knight in black armor and man sized sword is a bigger threat.
Oblivion will often have dudes that visually and behaviorally are the same, but hit way differently because of the numbers assigned to them. You can’t really look at a scene and understand what you’re getting into.
Other games also do a bad job here. Borderlands for example will have identical looking bandits, but in this area they’re indestructible level 100, and that one they’re push over level 5. The ass-creed Viking one did the same thing. Archers on one side of the river you could ignore, but the far side would one hit you.
I think a lot of studios don’t want to invest in the extra art assets and stuff when it’s cheaper to just use the same monster model and assign it different numbers.
I’ve definitely had some coworkers that in retrospect we should not have hired. But I’ve also had people I was iffy on that turned out great. Hiring is hard.