Yes but in these sports the 6th best team in the regular season never misses out on the postseason, which is essentially my point, to have 10 qualify for the postseason and not include the 6th best team doesn't make sense.
It can happen. Washington made the NFL play-offs last year at 7-9 whilst Arizona missed out on 8-8. Seattle made the playoffs with a losing record in 2010 whilst two 10-6 teams missed out.
Not very often admittedly, and it's a kink where some divisions are stronger than others. But it works, as it gives more teams prolonged interest in the competition.
You are never going to have a perfectly fair system. But a structure where everyone has something to play for has to be better than what's there currently.