I think you mean "prestigious" rather than "major accomplishment". You're right, there was a small period of time when it was. However, that window didn't quite align with "best time to do YC" (several years prior to such prestige) nor with "best time to be doing YC" (the prestige embellishes your resume, which is useless if you're otherwise occupied).

It's interesting to me that YC has managed to dilute this prestige to a large extent. I don't think it's an inevitable result of scale: look at Google. I think "Xoogler" prestige has diminished, but it's not nearly as bad as what has happened to the YC label.

My theory is: YC never figured out their formula. The whole formula is essentially Paul Graham, who had a knack for trusting his gut (and sometimes his wife) when everything else in his "system" was saying NO.

Once they lost that, they had to rely on what was left, and it simply wasn't competitive anymore. It's like Apple in their John Sculley era. While Sculley is credited with growing Apple's revenue from $800 million to $8 billion, his approach created a "mess of dull SKUs" that eventually confused customers and diluted the brand.

They also have a (bad) habit of removing access to bookface for all the founders who aren't "active", decimating their network and in some ways discarding valuable knowledge around what didn't work.