No matter what the format for determining a national champ, there will always be teams with a legit argument that they got screwed.
This is true, and also a big reason to go to 8 team playoff. while a 9, 10 team may still have a reasonable argument to be included, it would be much less relevant than a close 5, 6 team has in the current landscape.
Most years it will be clear cut and a big separation between the top 4-6 and everyone else. Very rarely could a 9, 10...really have a case.
This year, overall, its a pretty big gap between #1 and everyone else.
Also, with only 2 playoff games, there is more of a chance a team could simply get huge breaks and catch fire for 2 games....if you add that extra game, in my opinion, you get a better representation.
Look at last year, pretty clear that Alabama and Clemson were the best 2 teams, and Stanford probably should have been in over MSU, and probably Oklahoma. 8 team playoff would have sorted all that.
Side note, would love to see a Western Michigan(or non P5) get a crack. Sure, they have little shot, but I'd like to see that game over a fringe #8 P5 team.