Once you alienate the diehard/core fanbase, you're going to have little ability to attract the casual fan.
This is going to be a unreasonably lengthy semi-tangent post in 3 week old thread.
First, auto racing and golf in America have this problem of looking around the sport's landscape and seeing how well playoffs and tournament play does for ratings. NCAA March Madness is huge and was probably the thing itself that led to playoff expansion even among the 4 major sports leagues. Baseball 'postseason' was AL champ vs NL champ in the World Series. NFL Playoffs didn't exist, the Super Bowl was the AFL/AFC vs NFL/NFC champion. I don't know what basketball and hockey used to do, but I would bet that it didn't involve taking out only half of the teams that just played 82 games against each other and making the rest start over now that those results are meaningless.
Granted some of this is unavoidable because of league expansion. This was possible in 16 team leagues, not as likely in 30-32 team leagues. But now you have the ridiculous scenario where nearly or fully half of the teams in the league make the playoffs/postseason. Baseball is currently the lowest ratio despite recently adding 2 more teams and stands at 10 of 30, 33% (and I will admit I like how they did the 2nd Wild Card by devaluing the WC over the division winners). NFL is 12 of 32, NBA is 16 of 30, and NHL is 16 of 31. Those last two are especially egregious because they play playoff series that seem to be interminable. Hockey has about 2 months of true off season for the teams that play in the finals.
Anyway, the result is that Nascar has tried to shoehorn some sort of playoff nonsense into a sport that doesn't need it. Look at what adding playoffs did for college football national championship clarity. Not a god damned thing. Fans don't want this shit, advertisers do, leagues do. Nascar is just doing a particularly poor job of selling their changes so it is notable.
Second major point and why I quoted DK's sentence above. To a much smaller degree I feel like this statement is the NFL's current problem in a nutshell. Sure they were starting downhill from Everest while Nascar was starting from the top of the town dump, but both are losing viewers in my opinion because they tried to make their product mean something to everyone. The early 2000s-ish boom for Nascar was a total illusion. It brought a wide variety of people in. Money to travel and camp at races was there, people were spending. Now they think that period was 'normal' for them and they are trying to recapture that wide audience. In the process they made the core product worse and are losing the fans that were there in the 80s.
In the case of the NFL, a large segment of the viewing population watch because it is a social thing to do. They might not particularly care about the team or the game but you get together with friends, eat and drink for a few hours, and ostensibly to watch a game. It is largely or entirely because of the handful of people in that group that actually like football, the rest are along for the ride.
Now, make football terrible to watch, insert all sorts of human interest garbage into excessively long breaks from game action, stop play constantly to review god know what. If you lose that core viewer, that isn't one viewer, that's five or 10 people with them that aren't going to watch if they aren't serving brats and beer on Sunday.
Soccer quite honestly might be the only saving grace for sports in this country and if it has to be the EPL to save American sports, then so be it. Congrats to them for keeping a lot of the garbage that has infected American sports out of their league. At least I can watch a fucking game in under 4.5 hours.