She also lists several legitimate reasons to turn down the role. She didn't want to move to London and get painted green every day for 6 months, which Saldana and Bautista have both complained about (the make up, not London).
Other than that, this seems like she's admitting to making a huge miscalculation, picking A Million Ways to Die in the West instead.
As stupid of a decision as this appears to be in hindsight, Seyfried wouldn't have been as good in the role. It's entirely possible that with her in the role, the movie might have flopped.
I think the only egregious thing is thinking that being in an MCU flop would negatively impact her career. The Incredible Hulk was technically the first MCU flop, but I'd argue that Eternals was the first one that failed on its own merits. That entire ensemble cast hasn't had any issues getting additional work. If anything, it's the successful movies that resulted in actors being typecast and struggling to find work.
So the takeaway seems to be that you shouldn't let fear keep you from projects. Choosing other passion projects, not wanting to be in makeup, not wanting to move, those are legitimate reasons to turn down a role.