During the entire 4 team and now 12 team playoff era I've always been fine with SEC getting more teams than other leagues. It's just the best conference the same way the Big 12 has pretty easily been the best basketball conference for over a full decade.
Big Ten has to prove to me that they're significantly deeper than the top 3-4 teams. I've never seen it and every year the data grades it out. There were lots of years even the Big Ten East on its own graded out as weaker than 10 team Big 12, throwing in the west there wasn't a single year the past decade the Big Ten had better football.
The hard part is that in terms of a playoff, that depth of the league is great, but you're way better off being an OK league with a few teams that are way above the rest rather than a great league that's all mucked up. Even if the SEC is clearly better than the other leagues, and might justify getting 5 teams in based on overall strength and thinking that's the right proportion of the playoff, if the 5th best team is only 7-5 because, say Alabama, Georgia, Texas and Tennessee all win 9+ reg season games, then they probably are only getting 4.
To me there is also an important approach to the playoff that I think needs to be used. To me the idea of the playoff is not to get the 12 best teams in. It's to make absolute sure you are getting the best 8 or so teams in. The reason that is different is with unbalanced schedules we really can't say with certainty if some 13-0 G5 is the best team or 15th best team. But we can say that if you finished 4th in your league, you aren't the best team in the country. You might get hot in a playoff and win, but you aren't the best team.
So make sure you get the best 4, 5, or 8 teams in. But after that, if you aren't sure err on the side of accounting for unknowns and uneven schedules.