Apple TV+ Buffering Constantly and only Apple TV+

I have business grade 1.2 GB service with only 3 devices on right now and the buffering is substantial. I get 2 seconds of frames and 5 seconds of lag fairly consistent.

I tried the step, but it did not work for me. Every show freezes and looks like a slide presentation when it buffers

Mine speed right now is 700mbps dedicated through Ethernet instead of WiFi and it does the same thing

I ****** because I have friends over to watch my Apple TV and it will not play !!why is this

Welp -- I did find a workaround:

I use the Apple TV application on my Macbook Air to do the actual streaming part (i.e., to get the video and audio off the internet). Then I use AirPlay to connect to my Roku. Turns out that when you watch Apple TV on a Macbook, it pops up a window for watching stuff, and that window has an AirPlay icon in the lower-right, so that only the Apple TV content streams to the Roku (i.e., it doesn't just mirror my laptop's whole display, it correctly sends the Apple TV content and uses the full screen on my TV). Also, in that state, I can use my Roku's remote to pause the show (i.e., I don't have to use the laptop to pause and resume).

From this we learn two facts, which are related:

1. There's no bandwidth issue and there's not actually a problem at the Apple server end, since with the right combination of hardware and software I can watch Apple TV at my home.
2. Therefore the problem must be with my Roku and the other streaming devices I've tested. Is it the Roku app? Is it that my Roku is kind of old (hence the current app may have problems with my old Roku)? Don't know.