Sign stealing starts in little league where you encourage your players to figure out the sign for stealing or what put his coming.
If you think they are stealing your signs you change up your signs. All of these pitchers should change signs regularly and especially in high leverage games. If they don’t then they should assume they are being stolen.
If the Astros were the only team to do this it would be one thing but the Yankees have done it the Red Sox have done it and nobody is out to crucify anyone but the Astros for it.