Given that you have already reinstalled iPadOS - and restarted your iPad - the issue may perhaps be due to your WiFi Network/Router settings, or your iPad settings having unexpected difficulties with your Router setup or ISP.
Recommended settings for Wi-Fi routers and access points - Apple Support
As an initial step to localise the cause, try joining a completely different WiFi/Internet connection. If the iPad performs as it should when connected elsewhere, the list of possible causes becomes much shorter. By contrast, of the problem persists with other networks, then we need to look closer at your iPad setup.
Have you tried connecting to your iPhone hotspot - this being an alternative internet connection to which you have immediate access? Perhaps a friendly neighbour will allow you to “borrow” a WiFi network connection?
A simple restart of your WiFi Router may also be worthwhile - as the Router can often impact performance of one device while other devices may appear to offer expected performance. To restart you home router, disconnect power - then wait at least 30 seconds before restarting. When you router has rebooted (which may take several minutes), force-restart your iPad:
- On an iPad with a Home button: Press and hold the top button and the Home button at the same time. When the Apple logo appears, release both buttons.
- On an iPad with Face ID: Press and quickly release the volume up button, press and quickly release the volume down button, then press and hold the top button. When the Apple logo appears, release the button.
Are you using the new WiFi Private Address feature of your iPad? This feature is intended to provide additional privacy and security when using “public” (untrusted) WiFi networks.
Settings > WiFi > [Your WiFi Network / SSID] - tap the “i” icon - Private Address
The Private Address feature is largely unnecessary for your home WiFi network; if enabled, Private Addressing can have unanticipated consequences and/or interfere with operation of some services. If only as a diagnostic test, you may need to disable this feature. Private Addressing can be enabled or disabled for each individual network.
Use private Wi-Fi addresses in iOS 14, iPadOS 14, and watchOS 7 - Apple Support
