Good coach at Memphis does not necessarily translate to power 5.
Virginia Tech, USC, and Notre Dame would argue otherwise. Fuente had VT playing for the ACC Title in his first year and in Top 25 this year. Clay Helton was our former OC in the last decade. Notre Dame hired away our OC last year and the only thing he's done is make them a Top 15 team after 4-8 the previous year.
Memphis is 4-2 vs Power 5 in the last 4 years. Memphis has a difficult time getting Power 5 schools to play us, especially given the current climate. Tennessee still owes Memphis a home game that they "delayed" during the Deangelo years. Same for Arkansas.
Contrary to popular belief, there are a handful of G5 teams that would beat handily 2/3 of the Power 5 schools.
Watch the UCF/Memphis AAC Title game this weekend. Actually use your eyeballs, be honest with yourself, and tell me those two teams wouldn't beat every team in the SEC East except for Georgia and every SEC West team except Auburn and Bama.
True that if UCF or Memphis played an SEC schedule, they'd have 2-3 losses. Know what that would make them? - record wise equivalent to Auburn, LSU, Mississippi State, but doing it with 1/10th the budget.
Memphis and UCF are chock full of 4* and 3* players. These aren't a bunch of plucky 1 and 2 stars that have been coached up. Most of these recruits had offers from Power 5 schools and would be getting playing time their Junior and Senior years at the likes of Oklahoma, Florida, etc. They chose to playing time over prestige.
They aren't destroying teams simply because of a "system". They are destroying them because the system is being run by superior coaches that have recruited and are coaching better athletes than their competition. If Norvell can recruit Power 5 type talent to Memphis (and Frost to UCF), why is it so hard for Vol fans to fathom that UT is an easier sell (better conference, better TV exposure, better facilities)?
The defenses give up more points because the offenses score at an incredible pace and don't give the D a lot of rest. However, the last time I checked, the team with the most points wins the game. I'll give up 40 points every time if we score 45-50.
Lastly, if Missouri can score 30-50 points on SEC defenses, I promise you Memphis and UCF could.