I left off the Missouri game. I don't think you can really fault Gonzaga for only playing 9 Tier-1 Games. It's going to be like that every season. When I compare their OOC schedule with teams in your 6-14 range, it actually looks favorable. Look at the NCAA Tournament teams that these teams played. Gonzaga played 6 and no one else I have listed below played more than 4 games. They had 3 losses, but they were to the best team in country in Villanova, a double OT loss to Florida, and a road loss by 2 to San Diego St. They also dumptrucked Creighton and Ohio State and went 20-1 in the West Coast. Eyeball test tells me that they were a top 10 team. Here are the OOC schedules against NCAA Tournament Teams for most of the schools you listed in the 6-14 range:
Texas Tech:
W- Nevada
L- Seton Hall
Purdue:
W- Arizona, Butler
L- Tennessee
West Virginia:
W- Missouri, Virginia
L- Texas A&M, Kentucky
Cincinnati:
W- Buffalo, UCLA
L- Xavier, Florida
Loyola Chicago:
W- Florida
L- None
Tennessee:
W- Purdue, NC State
L- Villanova, UNC
FSU:
W- Florida
L- None
Gonzaga:
W- Ohio State, Creighton, Texas
L- Villanova, Florida, San Diego State
Why focus just on OOC? Teams play 30-ish games in the regular season. Teams like Gonzaga and Loyola have to schedule big in the OOC because their conferences aren't all that good. Frankly, the same could be said for the Pac-12 the last few years.
Teams like FSU and Texas Tech are going to play 12+ conference games against NCAAT caliber teams. If they scheduled like Gonzaga OOC, they would play 80% of their schedule against NCAAT teams.
I saw Gonzaga play 5-6 times. Full games. They looked more like an 11-20 team to me. KenPom has them at 10th, which is absolutely the top end of where I would put them. 8th is simply too high. They don't own a win over a team that finished in the top 15 all season--including the tournament. Depending on how you view Ohio State, they might not even own a top 20 win.