Was this a blip year for Andersen or is he starting his 30s slide?
you were good on the argument until you threw in Carey Price.
Price 26-30: .927, .933, .934, .923, .900
Andersen 26-30: .919, .918, .918. 917, .909
As an outside observer, I think there's a big reason to believe this year was simply a blip.
You can look at Michael Hutchinson's absolutely abysmal numbers, and probably conclude that there were games last year Andersen played that he probably shouldn't have, simply because they had absolutely no confidence in their backup goalie. There were also likely games that he would have / should have been pulled, but wasn't for the same reason.
It's also not like his "down year" made him a sub .900 goalie... he went from .917-.918 to .909, and from the mid 2.7s to 2.85.
That being said, that's one of the great things about him having a 1 year deal -- you get to see what he's got in a better defensive environment, and then get to make a decision. You also get the benefit of him seeing this year's goalie market, and realizing that $8-9m is simply not on the table with COVID.
As for the Carey Price comparison, Andersen is .916/2.77 in 244 gp with 244 starts over the last 4 years. Carey Price is .913/2.62 in 235 games with 232 starts over the same period.