Don't let anyone tell you, othetwise.
If you do NOT want to upgrade/update your Apple mobile devices, you do not have to.
I did NOT upgrade ANY of my iOS devices for three full iOS versions as iOS 11 was complete and utter garbage.
I missed the last window on iOS 12 which was OK.
iPadOS 14, so far, has been the best release of iPadOS, to date, IMHO.
iPadOS 13 was a dumpster fire of constant issues AND, to date, iPadOS 15 is following the same course as the oldef iPadOS 13.
Apple iOS/iPadOS is following the whole odd/even Star Trek the original cast movies course where odd numbetr versions of iPadOS are NOT very good, but even number versions of iOS/iPadOS get all the prevuous odd version bugs/issues/kinks all worked out and an even number iOS/iPadOS runs pretty well throughout its entire update cycle!
If you do NOT want to upgrade/update ANY of your compatible devices to the current iPadOS version, then don't.
It is YOUR device to do whatever you want to do with.
I am, currently sitting out iPadOS 15 and have left all of my familiy's devices runnning iOS/iPadOS 14.8.
Everything still works and everyone is happy with having NO iPadOS 15 issues.
So, far iPadOS 15 is, currently, just NOT very good.
I say wait it out until later point release updates for an iPadOS 15.x, that is actually halfway decent, if this, eventually, does happen.
As iPadOS 15 is, currently, still too early and it is still a mess.
If you just want to wait it out, just wait it out.
If your iPad is still doing everything you want it to do, DO NOT FEEL PRESSURED by others here to tell you what to do and make you feel you HAVE to upgrade/update your devices and computers.
Apple is more like Microsoft, for quite some time, now, foisting bad OS upgrades/updates and using its user base as OS/software beta testers.
You just do you!
If you really do not like the currrent state of iPadOS 15, then you do not have to upgrade/update your devices.
What everyone forgets to tell users, is that Apple iOS/iPadOS upgrades/updates are one-way ONLY! Forward.
So, if you do not like an iOS/iPadOS version upgrade/update, there is NO easy way OR NO WAY to revert back to your devices's previous iOS/iPadOS version.
You DO what feels best for YOU and your device usage habits.
If you are fine with the iOS/iPadOS your iPad is, currently, running, then just leave it as is.
The decision is yours and yours only.
Best of Luck to You!