Too squishy or wimpy for what? Who cares about CR, it is meaningless nonsense anyway, and as monster creation rules do not even exist in 5.5. there are no benchmarks to meet. Just represent the creature consistently.
Too squishy or wimpy for fun use.
I already explained it.
PCs on the monster side punch way WAY higher than their defense. They aren't fun to use because they are not even glass cannons, they are paper cannons.
PCs deal a bunch of damage then instantly die
NPCs modeled after PCs are more like one shot traps like bear traps and falling rocks than monsters you fight. Because they either kill you then die or just die