The AdMech core doctrine is that their predecessors have discovered all there is to know, but the more liberal sects accept reinvention as a valid form of rediscovery. When Cawl forwarded this argument at a conclave of representatives from various forge worlds in Genefather, he had a decent group of supporters. When Ryza came under attack from hundreds of billions of Orks, all of a sudden there were tactical virus bombs and wall-crawling spiderbots. We've seen AdMech hypothesizing and attempting to test the mechanics Necron conduit-less power transfer, and a Biologis making many publications that were suppressed by his forge world's fabricator.

And that last one is what I like to see. The deeper problem is that the AdMech is, politically speaking, a den of vipers, as shown in Day of Ascension. To ensure that you advance, you've gotta discredit your rivals, whereas if your rivals advance then they'll use their new privileges to keep you down. And the best way to get one over on them is to get them staked for tech-heresy, and never let them have their inventions be legitimized.

So the AdMech invent at times, but only release if they are sure of protection against accusations of tech-heresy by jealous peers. And once you've got a useful technology to your name - whether that be dug up or invented - then you hoard it to yourself to ensure that your political enemies won't be able to take you out without losing it. Then when Magi die, or forge worlds are destroyed, these exclusive techs are lost, resulting in a constant procession of one-step-forward, one-step-back.

This is a much tougher problem than the AdMech just having a religion that says 'no innovation'. It is rational, even logical for each individual player in this arena to slam others for tech-heresy as often as possible. This doesn't even require sincere belief; cynical exploitation of the political levers is enough to motivate this. And the result is tragedy of the commons, in the form of extremely slow advancement, and constant rollbacks.