You might want a proper translation of his statement. Here's one I whipped up (for the one paragraph where he talks about it):
[Regarding the] European Superleague “There were informal contacts from some clubs, but we didn't give [them] much attention for two reasons. The first one being that the European Union does not allow a closed competition circuit like in the NBA, for example. Seeing as the Portuguese Football Federation (FPF) is against that, and seeing as FPF is part of UEFA, we cannot participate in something that is against the principles and rules of the EU and UEFA. If that goes forward, something which I highly doubt, UEFA is not going to end and they will surely continue having competitions. It must be recognized that the competitions that UEFA organizes are the official competitions. We aren't worried about being there or not, we're in the Champions and we hope to continue being there for many years"
In other words, he confirmed that Superleague talks were made off-handedly and informally, implied that it is a silly proposition, and his team's going to stay where it is thank you very much. He can be much more scathing than this if he wants to, but his brutal (and often shameless) honesty is always refreshing. Pinto da Costa is a borderline mafia boss, but he's our mafia boss (even if I'm more partial to Sporting).
To answer the rest of your (unvoiced and rhetorical) question, I don't think either Sporting or Benfica would accept it either. Though my opinion is based on stereotypes and preconceptions of those clubs, and as such, I won't elaborate further
The historical context @Zell provides is especially important, it meant that there was an appetite for reforms from a large chunk of the fanbase - I'm sure there must have been some opposition to the formation of the Premier League but there was absolute a remit for reform whereas there is no appetite among the fans, players, pundits, managers for a creation of a European Super League, it is quite blatantly all driven by the boards of the biggest clubs who want a bigger piece of the pie.
I am so incredibly disappointed that a club that I love and hold very close to my heart have done this. Can't say anything other than gutted. There have been rumblings about this for some time, but following the news yesterday...it just felt different. Like this was inevitable. Absolute greedy bastards.
I hate the sound of the Champions League reforms, but I hate the sound of this so-called Super League even more. It's elitist, it's cynical, and it's come from a place of greed and disloyalty that I just cannot get behind it. It's ultimately so disrespectful to the other clubs in the country. I am far from a fan of Leeds United, but that club have played their way into the Premier League and have earned the right to compete against the best in the country. The same goes for Leicester City. They have grafted and have worked to get into the top tier. The idea that the "big" clubs can just cart themselves off into a league where they cannot be relegated or displaced is absolutely disgusting. They are building a wall around the top 6 and are effectively saying to the other clubs that they're not invited. Even the idea of having those 5 extra teams coming in on a rotational/merit basis isn't enough because of the other immovable teams. It's not coming from a place of merit or fairness.
The fans of the game are the very last ones to be consulted on this and they have been dropped this bombshell without any input being asked of them. It's wrong. It's their club. These players, managers, chairmen, boardroom people, the suits, they all come and go, but the fans are your one constant who will always remain and stick with the club. To do this is just taking the absolute piss. We're living in a time where fans can't even get into games due to restrictions, and now this is how they're being treated by their clubs. I also feel for the fans of the teams outside of the top 6 because they are being treated with proper contempt, that their clubs are simply not worth playing against because the so-called big teams only want to play against the other "big teams". It's vile.
I feel that a lot of damage has been done already and it's a huge moment for the sport. It's very unsavoury. I echo every single word of what Gary Neville said because he was speaking as a fan of a club that he clearly loves, but also as a fan of the game. The way that we are trying to load the game by tilting it even more in the direction of these bigger teams is just plain wrong. I cannot and will not get behind this idea. If UEFA/FIFA/whoever decide to deduct points or ban us from domestic or European competitions, then we completely deserve it.
I've already said a few bits and pieces in WhatsApp groups, other forums, social media and so forth, so apologies if this doesn't make too much sense as I get that it's quite ranty. I'm pissed off. Where's the game that we all grew up with and loved?
Another key difference with the formation of the Premier League was that it had approval from the FA.
English football was in dire straits in the late 80s. Crumbling stadiums, rampant hooliganism, poor public image, declining attendances, English clubs banned from Europe etc. It was felt that England was falling behind the likes of Italy and Spain and the big clubs advocated the new league to help rectify the situation. They also needed more money to improve stadiums following Hillsborough. At the time the Football League (different governing body to the FA) managed TV rights (ITV at the time) and distributed the income to all 92 clubs. The TV deal wasn't that lucrative and so as an independent body (the Premier League) they could negotiate a much better TV deal with Sky. The FA didn't like the Football League at the time so was happy to allow this to happen. They also felt that it would help English clubs compete in Europe and improve the game's image.
So the formation of the Premier League at least had some other postulated benefits outside of enriching the bigger clubs. It was also essentially a reform of the football league system rather than a true breakaway like @killthenet has said.