Since 2015, they have 11, 12, 10, 12, 12 wins, and 4 straight division titles, with all 5 seasons resulting in a playoff berth. Mahomes put them over the top as an elite offense, but they were a very good team before he took over.
That predates Mahomes, and Ried has never been one to prioritize defense, so your statement would seem to be false.
Aside from that, even trying to argue that, as a team, the Phins as now constituted, are in any way comparable to KC over the last 5 years is ridiculous.
I'm not arguing your premise, that a great QB can make a huge difference, absolutely they do.
The specific example you are using, however, is laughable.