To the OP, what you see as a problem is actually a feature of 5E, and one of its strengths, according to its advocates. Consider that in most versions of D&D--certainly 3E and 4E--monsters quickly became fodder when PCs levelled up beyond a certain point. 4E tried to partially rectify this by having, for instance, steroidal orcs and such, but it led to mixed results. 5E has effectively made lower level monsters remain threatening well past their former sell-by date, so an ogre is always--or least for a good while--scary and ogrish, rather than becoming some kind of massive inflatable ogre-shaped balloon.