I have a 10.5 iPad Pro which still performs well. I don't need to upgrade for performance.
I read quite a lot on the iPad and I wonder if the experience will be (even) better with the new iPad Pro 11.
You would get a slightly bigger screen. If you can afford it - why not. You can also enjoy the ’quality of life’ upgrades of CPU, RAM, camera, Thunderbolt, Face ID etc as well.
There's nothing 'wrong' with the 10.5 Reading on the iPad for longer periods of time is not that comfortable on my eyes and I wonder if the 2021 screen is any different and maybe worth the upgrade in that regard.