I don't object specifically to the 10-6 national champion, I just object as a fan who wants the best and most entertaining product on the field. I'm pretty cool with the "best" team from each P5 conference getting in, though imagining the ACC without Clemson is a scary thought as far as eating up a playoff spot. It's just that most conferences aren't designed to send their "best" team. There have been a few articles lately about the bigger conferences abandoning divisions, going to pods, and making their title games 1 vs. 2. That would ease my concerns.
TL/DR: 2/3 of teams in conference title games aren't ranked in the top 10, so it isn't a fake scenario. 9 times in 30 ACC, B1G and PAC title games, almost 1/3, NEITHER team has even been in the top 10. OOOH PLAY IN GAME.
The data:
2003 KSU is a better example of a meh champ than 2001 CU. CU was 10-2, while KSU had 3 losses in the reg season, including to Marshall.
One thing you're missing is that many of these conferences only recently started doing championship games, which opens the door to bullshit champions like 2012 Wisconsin, which was 4-4 in conference, 7-5 in regular season.
Rankings in the ACC title game since 2005 with winner bolded:
22 vs. 5 16 vs. 23 6 vs. 12 25 vs. 18 12 vs. 25 12 vs. 20
5 vs. 21 13 vs. NR 1 vs. 20 2 vs. 12 1 vs. 8 3 vs. 19 1 vs. 7 2 vs. NR
Obviously since 2014, there has been an elite team which has saved the bacon by going unbeaten, but I count 3 of the 14 games which aren't silly as a play-in game, and this year will be 3 of 15 as it will again be top 4 vs NR. Six times in an eight year span, the ACC would have sent a team into the playoffs that wasn't in the top 10, and 5 of 14 games have neither team in the top 10.
The B12 has only had two winners of its title game not be in the top 10 - Texas in 97 and KSU in 2003. However, in 12 of the 17 years, one of the teams wasn't in the top 10.
The PAC has had two straight title games with neither team in the top 10 and a non-top 10 team has been in the game 6 of the 8 years. 2 non top-10 winners.
The B1G has had a title game with neither team in the top 10 in 2 of the 8 title games so far, and a non-top 10 team in 4 of the 8 years. 2 non-top 10 winners.
The SEC has never had a title game with neither team in the top 10, and a non-top 10 team has been in it 17 of the 27 years, though the non-top 10 team only has won 2.
So total there have been 13 teams win a P5 title game without being a top 10 team. Not counting SEC, that's 11 out of 47 years, so about a 1 in 4 chance of a non-SEC P5 champ being outside the top 10, so we could estimate that roughly every season we have a non-top 10 team in the playoffs, with some seasons obviously having none and some having 2.
A non-top 10 team would be playing for a playoff spot in 13/18 ACC title games, 12/17 B12, 6/8 PAC, 4/8 B1G and 17/27 SEC. So 52 out of 78 teams (67%) in these "play in" games aren't top 10 teams.
Also, when the top 5 team loses to the trash team, that top 5 team now eats an at-large, so you end up with actual top 10 teams being left out of wild-card battles. It becomes worse if we lock in a G5 spot, rather than have it qualification based.