4e math was roughly +1 per level. With combination of proficiency bonus, equipment bonus, and stat boosts.
5e math is roughly +1/2 per level. i.e. 4e/2.
And the 19th level caster nearly auto-hits the 7th level monster and takes it out with any control effect. And then you end up with things that are more easily handled than 4e minions by casters. Which is boring.That means any creature a few levels below/above you can't hit/miss you.
If the scaling is reduced to say... +1 every 3 levels. Then a 7th level monster can still hit a level 19 PC, just not as often.