That's weird. I have an 8th Gen iPad, the slowest device that can run iPadOS 26, and everything is fine on that old thing. (except the OS takes up the majority of the storage)
Interesting. Might try a factory reset then and see. There's noticable lag for me, it's especially slow when switching apps or bringing up the keyboard, as well as on first unlock. Interacting within a single app is still fine, it's interacting with the OS that's really sluggish.
8th Gen iPad is about the same on iPadOS 26 as 18 for me, which is slow. The 32GB really handicapped it for even being usable as to even upgrade it, I have to factory reset it first. I'm replacing it with a Mini.
The iPad Air 13 with a M3 is a really nice experience. Very fast device.
weird, my iPaid Air 3 which should have the same specs has been really for at least a year. Plenty of free storage, not so many apps, all visual enhancements turned off.