Nah, you misunderstand me. I think the NFL does have parity. But it’s hard to argue that MLB doesn’t when they have had a larger number of unique champions over the last decade.
As far as the quote about why bad teams often make bad moves, I agree completely. Check out the chart here and consider that the absolute worst player charted is the starting shortstop for the Royals - one they actually traded for. For bonus points take a gander at where their new Catcher is… 
I don’t disagree with any of this, actually. And that is certainly a valid way to measure “competitiveness”.
Based on this metric I tried running the numbers for the NBA just for a comparison and found that those large markets you defined had roughly the same rate of making the playoffs as the smaller markets, so obviously the salary cap does have an effect on at least this method of measuring competitiveness, if not on the ultimate outcome of the season. Ran out of time to try it for the NFL but I wouldn’t be surprised to find results similar to the NBA.
I’m not opposed to revenue sharing in general, as long as it is accompanied by a strong salary floor. If it’s just a mechanism for keeping down players salaries then that is where I draw the line. I pay good money to watch the players, not to line the owner’s pockets. Also, any shared revenue should be tied to market size, not to payroll.
Just to be pedantic, obviously this is not true; eight teams won the World Series in the 2000s; the Yankees twice, Red Sox twice, Diamondbacks, Angels, Marlins, White Sox, Cardinals, and Phillies. And therefore, four of the ten titles were won by the two biggest payrolls, the Yankees and Red Sox.
Using the list of market sizes in the blog linked by the OP:
I like the idea of the hometown team - the team that scouted, drafted and developed the player - getting a discount on resigning a player. But how do you prevent a player from getting locked in to a city that he legitimately doesn’t want to play for? Maybe he doesn’t like the management or ownership or climate or whatever.
In the author’s example - he assumes Mauer wants to stay in Minn but will be overwhelmed by a large offer elsewhere. What if Mauer wants out of Min, even if it’s for less $$? How do you implement a system like this w/out overly restricting player movement? Or do we just not care about the player’s wishes as long as he gets paid?
The Yankees have won 103
89
94
87
101
101
103
95
87
That is the wins the last decade. Who is going to match that? Nobody can guarantee a World Series win, especially since the first series is best of 5. But you have the best chance in New York Shitty.
I don’t dispute that, or any of the other factual claims made in this thread. Obviously being in the larger markets will make it more likely your team will be successful.
The first point I was trying to make is that poor management has at least as much of an impact as market size. This easy to see by comparing teams in similar markets, or of similar payroll, and seeing the vast differences in both how they are run and how successful they were over the last decade.
The second point is that the proposed solution might not even solve the purported problem. The NBA has a strong salary cap both on team payroll and individual salaries, and yet had fewer unique champions than MLB over the last decade. I also believe I have seen numbers that indicate that the popularity (both TV and in-stadium) of the NBA has declined while MLB has risen over the past few years.
Another point I would propose, although perhaps not wholly endorse (I haven’t really given it full consideration), is that perhaps the largest markets winning the majority of the championships is not inherently bad for a sport. Those large markets do have the majority of the sport’s followers. And many of the world’s most successful leagues have far less parity than MLB - consider the EPL, where the top 4 teams have been the same for the last, what, 10 years? And only 3 different teams have won the title since 1995 or so.
Is it possible that what is good for the league as a whole might not be what is good for fans of the KC Royals?
This. I think fans of the small market teams need to feel that they have a legitimate chance to compete if they play their cards right, and to keep a good team together if they do manage to assemble one, so I think some financial reform is indicated.
However, there is no doubt that from the point of view of selling merchandise and keeping TV ratings high, it is better to have a higher likelihood of a Cubs-Yankees World Series than Padres-Royals in any given year.