Literally the only people who think the parks are competing are enthusiasts. The general public does not care. Cedar Point getting media coverage does not take away from Magic Mountain’s attendance, because the average visitor to each park likely has no idea that the other exists. They’re separated by two time zones and thousands of miles.
Besides, Cedar Point’s whole schtick is having the biggest and baddest coasters of their kind, not having the most. That’s why all of their new coasters in the recent past have broken records for their respective types. They aren’t worried about Magic Mountain, and vice versa.