setting aside the Yahoo piece -- its a polemic, and should be treated as such --
I do think that the NFL for coaching and front office jobs has operated as a informal network or guild ( similar to other entertainment businesses) that is very hard to penetrate without "a sponsor" to get you in.
Just look at all the family links around the NFL. As an example, Sean McVay is John McVay's grandson. Think Sean gets his first low level staff job if he didn't have that connection? He had to be competent to get where he is now, but that first chance was also really important.
Further, this is a really small pool of jobs ( ~350 coaches, ~200 FO people) overall, and the pay is
very high. Even position coaches make $250k+ per year -- making them a top 5% earner overall in the US, and if you advance from there, it just goes way up.
So lots of competition to get in -- maybe 20-30 entry level openings a year. You need to be really tight with someone on the inside to get the chance. Even if all the players in a network like this were 0% racially motivated, it likely produces results that are racially disparate (or said differently -- it would produce a near mirror image of itself), and its clear its not 0%.
I think Rooney rule has helped, but its a top down approach that doesnt address (AFAIK) entry at the bottom of the guild.
one last thing: hiring KK was totally going outside the rules of the guild, and i think that is a motivation of the criticism.