I think the iPad lineup is victim of Apple's pricing structure and their Quest for Margin.
The Air and, especially, the Pros are already so expensive that significant updates would drive the base prices even higher (an 11" MiniLED Pro could easily be $999 and the 12.9" could hit $1249-1299) and with a worldwide recession waiting in the wings, those prices could result in significant sales contraction, so at this stage better to keep them effectively "as-is" and look to get folks who did not replace their 2018 and 2020 models when the M1 model came out last year.
IMO, Apple should have just killed the iPad Air and positioned the 10th Generation iPad in that spot, giving it Apple Pencil 2 support and adding the P3 fully laminated anti-reflective display from the Air. That would have allowed them to raise the price to $499 instead of $449 and then they could have dropped the 9th Generation to $299. But I am sure they make more margin/profit off the Air than the iPad 10 so they want it around to try and, IMO, sucker buyers to upgrade to it.