I use an iPad 2 and the YouTube app works just fine on my iPad 2.
Make sure all of your apps are up to date, including YouTube.
The current YouTube app is STILL compatible with iOS 9.3.5.
Take a look a my tips here to help optimize performance of your iPad 2.
How much free data storage space is left on your iPad?
iDevices need to always maintain, at the very least, between 2-3 GBs, OR GREATER, of free data storage space.
In Settings app, General settings panel, turn OFF Background App Refresh for any apps you feel do not need constant data updating/Internet updating in the background when not using the an app OR turn OFF Background App Refresh
entirely/globally for the entire device.
Do the same in the Settings app under Notifications.Turn off notifications for apps you do not think you need notifications for and/or edit the different ways you receive notifications to help with performance by not always using all the notification methods together.
In Settings app under Mail, you may want to set a longer fetch time or set your iOS Mail app to only manually fetch your mail ONLY when you launch the iOS Mail app.
In Settings app (NOT from the iOS Control Panel) turn OFF
Also, in general, if you want a faster IDevice, on all of my iDevices, I turn off most of the iOS motion graphics eye candy,
by simply turning ON Reduce Motion in Settings app, General, Accessibilty settings.
Make sure you aren't running 30 to 50 OR A WHOLE LOT MORE background apps in the iOS 11 Control Panel/App Switcher.
If you are, you need to quit the bulk of these background running apps by tap and hold a finger on an app window in the switcher and slide your finger upwards to quit an app. You should be able to use more than one finger to quit more than one app window simultaneously.
Also, make sure you don’t have 20 OR A WHOLE LOT MORE of active website tabs running in the web browser.
If you do, greatly reduce the amount of active website tabs your web browser.
The iPad 2 ONLY has a paltry 512 MBs ( NOT GBs ) of internal RAM.
Any large amount of background running apps or active processes that have to constantly go out to the Web to fetch
data ALL THE TIME is going to slow down ANY iDevice and CAN, also, negatively impact battery life.
Some minority of user have been turning ON and leaving ON iCloud backups continuously backing up on a constant and daily basis.
If you are one of these users, in Settings App, tap your Apple ID, then tap iCloud, then find iCloud backup and turn off iCloud backup and only turn this on to do daily backups either when you are not using your iPad for a prolonged period of time (like when you are sleeping), then turn iCloud backups OFF when actually using your iPad.
OR
Only perform your backups on a lesser time schedule.( like twice a week, once a week, once every two weeks, once a
month, etc.).
In addition to all of the possible fixes and solutions presented, I suggest go into Settings, General, Accessibility, Increase Contrast and turn ON Reduce Transparency.
Your iPad won’t look as pretty, but iPad speed will improve considerably.
If you don’t like this look, then, turn OFF Reduce Transparency, but the additional speed boost will go away, as well.
Also, I would STOP using that 2-2-1/2 year old Safari web browser, as it is, probably, not safe and secure to use any longer, and seek out a third party web browser that is STILL currently being updated and STILL being supported on iOS 9.3.5.
Here are a few third party web browsers that I know are STILL being updated and supported on iOS 9.
Perfect Web browser
iCab Mobile Web browser
Dolphin Web browser
Aloha Web browser
Maven Web browser
Maxthon Web browser
Opera Web Browser
Good Luck to You!
