I've never argued our 2-5 rotation is better than yours- only that it would not be a fluke if it ended up being better.
I was also very high on Pivetta before the year started. There are times when numbers don't tell a whole story of can not be good for projecting future production.
Certainly several of your SP'ers have some very nice aspects, but I would not be making definitive judgments based on 6-8 starts- not for Kluber, Richards or Pivetta. Kluber sure looks like he's rounding back into form, but it's just 7 starts.
I'm not projecting Pivetta to end up as our best starter, but I do think he can end up with some very nice #3 or 4 numbers. He could suck, too, as could just about any Yankee starter not named Cole. No, I don't "know" Pivetta can't sustain being good. This good? Very likely not, but not impossible. You act like no pitcher has never blossomed later in their career, and it's not like he's 33. Scouts and top baseball people have always spoke of his abilities. Is there no chance he can't put it all together, this year? You cat like it's a 100% sure thing.
When it comes to Taillon, I've "talked about him" more than anyone- even Yankee fans. (I wanted the Sox to trade for him.) He's no sure bet- just like all the Sox starters not named Erod. What bugs me most is that you switch up criteria to suit each different starter. With one guy, it's most recent numbers. With another, it's their best WAR season. With another it's improved K and BB rates. With our starters, you selectively choose the worst aspect of their record or recent production or ignore or pooh-pooh their most recent numbers as "unsustainable."
If I had to placer a bet on which starter group beyond their #1 does better in 2021, it would be a very tough choice. I'd probably pick the Yanks, but in no way would I be acting like it's a forgone conclusion, and neither should you- "and you know it."