All third party app developers decides what iOS versions their apps will still support.
If older versions of apps, like the YouTube app, have either stopped functioning or have limited functionality now, then this is the way it is.
Do you really expect a 12-year old iPod Touch to be still have all very old apps to still be working and supported by third party app developers?
Also, you need to understand that these old iPad 2, 3, 4 and 1st gen iPad Mini models are nearing 8 and 9-years old, now.
As of the beginning of 2019, many, MANY third party app developers are all more quickly and completely permanently dropping older app support for all old 7, 8 and 9-year iPads that are running 2-3 year old and earlier iOS versions ( iOS 10 and earlier ).
Third party app developers are removing all of their older, legacy versions of their apps from Apple's App Store servers, now.
Third party app developers no longer want to support these 8 and 9-year old or older iOS devices, any longer!
Older versions of apps are, soon, going to be gone for good, now!
Getting older versions of apps for these old iPad models, initially from Apple’s iOS App Store is getting very difficult and very problematic and this issue is getting, painfully, much worse in 2020, now!
These old iPads are now reaching their complete end of life and support.
So finding older versions apps for older iPads, while still possible, currently, will be a tough challenge, now, in 2020.
Old iPads that can no longer be upgraded/updated will have NO MORE APPS AVAILABLE for initial download, at all, soon, from the Apple iOS App Store, for such old iOS devices in the very near future.
Older versions of apps for these older iPads will be completely gone, at some point, in the very foreseeable future.
Whatever apps you still have on these devices, many will still continue to work as they always have.
Those apps that solely rely on a regular, constant, wireless connection, to the Internet, for complete functionality, may stop functioning at some time in the future.
Again, it is what it is, today, in the year 2020!
So, this is really now the time to seriously consider a new or discounted, refurbished iPad from Apple or other Apple authorised resellers.
A lot has happened with iPad and iOS in 7-9 years, OR MORE and in the past 2 to 3-1/2 years since iOS 9 and 10 and much earlier iOS versions.
As an example and compared to your older iPads,
The baseline 2019, 10.2 inch screen 7th gen iPads have a 1/2 inch larger retina screen, newer, more powerful and nearly 2-1/2 times faster 2.3 Ghz, A10 Fusion processors, AT LEAST, 3-4 times the internal RAM, with the 2019, 7th gen iPad having 3 GBs of internal RAM, iPadOS 13 support, with much better and improved multitasking features, Apple Pencil and Apple Smart keyboard cover support and have better audio speakers and better/improved built-in cameras.
The newest 2017 iPod Touch is much more advanced, then your now, 12-years old iPod Touch you currently own, to the point of the 2017 iPod Touches being much more like an iPhone, now, without the phone part.
Once, again it is what it is.
Time to seriously upgrade all of your Apple mobile devices.
Sorry & Best of Luck to You!