Why aren't new vacuum tubes as good as old ones?

Whew! That's a relief. Thanks Wolf. Can you recommend a really good 7189?

My experience indicates that new tubes are as good or better than old tubes in most cases, and since there are new designs that hadn't existed before now it renders that argument moot for those examples. I use Psvane 12AX7T-IIs in my hifi and guitar amps that I believe are better than any old stock 12AX7 I've used, and KT120s are amazing, didn't exist until recently, and have been adopted as a standard tube by some heavy hitter amp companies. The myth of old tubes being better is simply silly...they may sound different, people might prefer them, but design, construction quality, and consistency is fine for new tubes from many manufacturers.

I use new JJ EL84s (7189s) in my Burriss Royal Bluesman amp, and they sound great.

Here's an interesting tidbit from the Atma-Sphere FAQ page:

"Atma-Sphere equipment is designed to work with commonly available tubes, making our products easy to live with. The 6SN7 tubes we use are produced in China but there are many aftermarket versions available. The output tubes are Sovtek, Svetlana or Chinese. The miniature triodes used in the preamps such as the 12AT7 and the 12AU7 are usually Chinese. Other types of tubes may be available on request."

I have no clue but based on what I know from what I hear I am with the wolfman on this. New tu.bes are not all gloom and doom like most new things are often regarded to be by audiophiles. I'm sureI can guess which side the sellers of expensive NOS tubes are on.

More audio twilight zone rumor accepted as fact.

Or, show us the facts to back up the assertion?

On off generalized observations have some value but clearly do not tell the whole story.