What exactly is stopping the federations and UEFA from banning these teams from their domestic leagues and UEFA competitions? Officials are whining a lot but not doing much, and there's only been talks to suspend SL teams to play at UEFA level. What's also official is that players who dare to play won't be able to represent their countries either.
Who knows what might convince the SL teams' executives that this backlash is not worth it, though.
For one thing it would be a massive legal mess. Banning them in the future is certainly a possibility, but they really need to wait for the right time to do that. If they were to do it immediately then it's an absolute certainty that all of the clubs would sue. Not only them either, but there's a significant chance that TV broadcasters and sponsors would sue too. If they paid however many billions to broadcast a 38 game season with 20 teams including some of the top teams in the world then surely they'd sue for breach of contract if suddenly a bunch of those teams got kicked out and the number of games was reduced.
They haven't done anything yet because they need to do everything by the book, they need a bit of time to research and plan how they'll respond rather than making a knee jerk reaction that will cause trouble for themselves too.
It could also be disastrous financially. Other clubs, including lower league clubs who are in a pretty dire financial situation with the current covid stuff going on, rely on money that's partially generated by those teams. I've seen people mention quite a few times that the lower English leagues rely quite heavily on the EFL Cup, and take the top teams out of that and the amount of money available decreases significantly. To be fair the EFL cup is also massively at risk with the new Champions League format coming, but at least with that they still have 3 years to try and work around it rather than immediately taking away a massive revenue stream which would be the case if they were to kick those clubs out right now.