Or just don’t deliberately inflate levels beyond meaningful power they can provide. Blizzard needn’t make level cap 100, when there’s no enough power increase after a particular level. Then, in effect, these levels become redundant, for they don’t achieve anything meaningful. They did this, probably, to prolong what’s already final and give an illusion of progress, but so inflated that you barely feel it.
As you say, they can smush all these paragon points per level that you receive and put a level cap at 70-80 and simply increase paragon points per level.
Inflating stuff devalues them. Inflating levels devalued their meaning of providing meaningful increase in power as each next level feels less impactful. Having redundant levels that you go through devalues their meaning.