so my older ipad with IOS 9.3.5 is a victim of planned obsolence and I have to buy a new one !

Your old iPad running iOS 9.3.5 will either be 9 or 10-years old this year, in 2021.

Apple ended support for all 8-10-year old iOS devices well over 4 years, ago, in 2016.

Third party app developers abandoned and stopped supporting these 8-10-year old iOS devices nearly 3 years, ago, in 2018.

There are, virtually, NO MORE third party apps available from the iOS App Store, any longer!

Third party compatible apps for such old devices are few and far between, now, in 2021.

It's 2021 now!

A WHOLE LOT has happened with iPad and iOS ( now iPadOS ) in the past 9-10 years.

You really need to seriously consider a purchase of a new iPad model OR a much, MUCH “newer” and less expensive, refurbished or used iPad models, from better known, trusted Apple product/device retailers/resellers, locally or online, capable of running the latest iPadOS versions.

There are PLENTY of newer, older iPad models that can run the latest, current versions of iPadOS.

I am sorry that you had to learn all of this, but this does not change any of the facts regarding these very old iOS devices.

Sorry & Best of Luck to You!

No, not planned obsolescence at all. Just the inevitable march of technology that outstrips the capabilities of older CPU and system hardware/architecture designs.

Nope.

No one is forcing you to buy anything.