I should clarify what I mean when I say higher level monsters feel scary in Pathfinder 2. I am not talking about features of their individual designs. I also do not mean 5th Edition monsters cannot actually be scary or have abilities that feel scary in play.
Fighting higher level monsters feels desperate because of features of the system. The tight math, scaling, and critical success and failure mechanics all work together so that the fight feels desperate independent of the individual monster design. Higher level monsters are much harder to affect, hit you more often, critically succeed more often, and criticals hurt like a lot. You really have to work together to take one down.
The inverse is true of lower level monsters. The same mechanics mean your spells and attacks are much more effective. You critically succeed more often. They critically fail their saves more often. Orcs start tough, but eventually you will carve through them like butter.
Independent of individual monster design the mechanics embed level directly into the narrative of the game.