I also have an iPad (5th Gen.) 2017, Wifi 5+Cellular and notice that especially when opening emails (in Apple Mail) with a lot of text and images, e.g. advertising from companies, the Ringli appears with “LOADING.. .” for a long time until the email is opened.
This happens on the iPad in my home WiFi from the IB3. When I connect the iPad via mobile data, the same email opens immediately.
On my iPhone 13, all emails open immediately, whether via Wifi 6, Wifi 5 or mobile data.
I am always connected to my iPad and iPhone at home via WiFi 5GHz. Wifi 6 on or off makes no difference. The speed test on the iPad and the iPhone always shows almost the same values: 240 down and 50 up.