Why do people say its spoiling?

[Zojha]

You'll get to play it your way for all eternity after those few days anyway.

So does the other side. In both cases, via party finder. Because that's what party finder is for: To make a group according to your and only your specifications. Want a full miqo'te run? You can do that. Want a guaranteed blind run? You can do that. Want a run where everyone cleared already? You can do that. Want a speedrun? Want a slow run? Both are possible! And anytime at that!

In duty finder, you don't get to make those specifications. And the most mature way to go about that is to ask who wants what, explain that you'll do a ready check as poll and what "ready" and what "not ready" mean in that context, then vote this way and go by majority. You can leave if you don't like the result, but please make a party finder next time. That's how civilized men and women would do it.

[Taika]

So does the other side.

The first few days are the only ones ever when it's possible to do blind runs for this content, so it doesn't really apply the other way around.