Voadam
Legend
My memory is that 4e monsters were fairly straightforward to run if you were running one or two types at a time. They have a couple options that are easy to see where they fit in tactically and are generally not overwhelming to run at the table but have decent options that make sense for the monster. When you get to running five different types in an encounter, and they have stuff like marking to track it can get to be like mid-high level 3e where you can lose track of parts of the statblock in a fight.4e stat blocks were meant to incline towards this (eg I remember reading a designer discussion of the Mind Flayer stat block along these lines).
I remember reading they were intentionally conscious of trying to make them easy for a DM to run at the table, with intentionality on graphic design to support this with everything on one page, most mechanics spelled out on the stat block, and designing the number of features and options with useability in mind.
I know that when I had my young son play monsters as PCs for one shots the strategies with the options were intuitive enough for him to really enjoy the experience.