I'm not even against Pro/Rel tbh but their system isn't all that great as most of the teams are poor, cash strapped, in debt, and there's a huge gap between the haves and the have nots way worse than the American way of doing things. So big is the gap that the "top dogs" wanted to split from the lesser clubs to form a Super League. Lets face facts, they'll always be shyt teams no matter what. There's no such thing as a good team without there being a bad team. Imo teams like the Timberwolves have been trying, the Kings have been trying. They just keep striking out in one way or the other. The lesser franchises in MLB are ten times worse. They literally dump players or keep their salaries to the lowest point possible. But the way the game is set up these days they can still win games and make the postseason like the Rays do. American leagues, mostly the NBA, is fighting for viewers worldwide as well and are up against streaming television just like the next guy. I've been to Europe & South America a couple of times and it was a different world from my point of view when there's no football, basketball, or baseball being discussed. Soccer/football runs the sporting world over there. That being the only big game in town and country definitely plays a part.
The gap between the haves and the have nots is by design. They intentionally impoverished the rest of the teams around them so they can pillage them. These same Super League clubs were the same ones (minus Manchester City) who lobbied UEFA and their domestic federations to implement the Financial Fair Play system which effectively discourages investment in clubs because they didn't want to compete in the transfer market anymore.
In England the Premier League only exists because Liverpool, Manchester United and Arsenal came together and influenced the rest of the First Division teams to break away from the Football League so they'd have to share less money with the teams below.
People look at Leicester City winning the Premier League as some miracle scenario but Derby County, Nottingham Forest and Blackburn were doing the same thing exactly 1 generation ago. Aston Villa and Everton were not only championship winners domestically but contenders and winners in Europe too. Leeds built a championship winning team within 2 seasons of being promoted from the Second Division. Newcastle got promoted, finished 3rd in their first Premier League season and spent the bulk of the next decade as title contenders and Champions League participants. If you're old enough to remember Jordan (which seemingly 4/5 of this board is) then your English counterpart is old enough to remember all of this or at the very least have a sibling who could. Now there's an academy system where the academies of the top teams can sign players from lesser teams for below their market value.
Parity existed these guys have done everything possible to take it away. You've been conned into thinking that these guys ran out of competition but they've spent decades colluding to suppress it.
In Spain and Italy the TV deals were heavily skewed towards these teams and the reason why they were even in those positions was because Milan were owned by a media company owner and Juventus and Inter have been toys for billionaires. Inter were also a toy for the fascist government. Even with those protections they were still match fixing and influencing referees. They were still cheating to hold other teams down.
The Spanish teams are instruments of state propaganda. Both Atletico and Real Madrid enjoyed state protection and interference at different points in time. Barcelona has had both money and political influence pumped into and used for their benefit by Catalan businessmen and politicians because they're seen as the sporting symbol for Catalonia. These teams are where they are because they've been propped up for decades for reasons that have nothing to do with football.
Even if you bring up UEFA corruption these teams are beneficiaries of UEFA corruption from the reformatting of the European Cup into the Champions League to the number of slots available per nation to the qualification and seeding process to Financial Fair Play UEFA has bent over time and time again to make sure these guys make money and keep their places now they just want to cut the middleman out. UEFA corruption has been mutually beneficial. The only problem now is the fact that they aren't guaranteed to qualify for the UEFA Champions League every year because teams in their domestic leagues are too competitive and keeping them away from the money. Juventus are the only Italian Super League team that have qualified consistently for the last decade, Milan and Inter (except for this season) had
been left behind and been irrelevant. The Spanish teams are consistently qualifying but the gap between them and the next team (Sevilla) is closing. Manchester City are the only English team in the Super League that qualified every year for the last decade the other 5 all spent times outside of it and Arsenal haven't even been in it for 5 years. Half of them aren't doing it on the field anymore that's why they were trying to change the rules of the game yet again.
You're coming in waaaaaaaay after the fact and saying no wonder these clubs wanted to team up just look at everyone else the system doesn't work but the last 80+ years (depending on the country) have been spent with businessmen, governments and administrators bending the system to benefit these teams. They're looters who were trying to run away and block any other team from catching up.