Have you tried your iPad Pro on another WiFi network other than your own?
Again, I ask, is this an Internet issue on Wifi or are apps that don't use Wifi slow, too!
IS your entire iPad slow or just while on the Internet?
Please be more specific!
Is your Mail app slow in retrieving email?
Also, ignore how the Apple website forums respond.
Apple has completely revamped/redesigned these forums and we are all experiencing some slowness on this site.
If your iPad is functioning normally on its own when not accessing the Internet, then there is a possibilty of a local network issue.
If you have any documentation or know how to access your MODEM/router's software, you need to to check its settings and maybe change the Wifi/MODEM reception channel to some other good reception channel other than channel 6 which most MODEM/routers are set to, by default.
You could, also, simply reset the MODEM/ router by just unplugging it for 30 seconds or so and plug the unit back in to see if this solves any possible MODEM/router issues.
Do you have anyone other family member that has their own local network setup to test your iPad Pro on?
You could take it back to Apple, again for another replacement, but before replacing it, see if your iPad has better speed on the Internet through the Apple Store's own free, public WiFi access.
You need to test your iPad on another WiFi network to see if the issue with your iPad is, FOR SURE, the iPad or your home network settings.
Good Luck to you.