I still use my iPad Pro 12.9” (2015) every day, and it is fast enough and eminently stable in doing everything that I want to do. Eight years is a good run, but I can’t help but think this is an attempt to force an upgrade at a time before the natural end of life of the device.
I will keep on using the device as long as the browser works, it just means that for some things like my taxes and my online banking I’m going to shift to other devices.