Look at Michigan's Adventure. This park has the highest profit margin in the Cedar Fair chain and hasn't built a new thrill ride since 2008. This is kind of dubbed as a "local family park". Why haven't they built one? Because their present business plan is working. Why build a new thrill ride when you're already breaking attendance records? You wait for attendance to start slipping then BAAM.
So what's Knott's doing? Basing what they're doing off records. Their attendance did better when they introduced family attractions so they're doing it again. According to Knott's website, there are 9 thrill rides (counting all under thrill rides tab & then the rollercoasters that would be considered "non-family". Only 8 if you don't want to count Screamin' Swing). There are 11 family rides under the family rides tab. That's not a very large margin at all.
Once again, not a saying a thrill ride won't be back, but the "family" direction is what Matt Ouimet wanted, and overall it is being well received by many critics (just not the whiney Facebook fans). But look at how well the chain did this year under that plan? Now he announced they're going to renovate all the Cedar Point resort and improve infrastructure at the parks that need it (including Knotts). He's all about the families and you'll see how good that'll do the park & chain over the years.
Also, families spend more money at parks than thrill seekers. End of story.