Youtube automatically switches to the lowest bitrate if it detects a slow network. Was it still too slow at 360p?
I used NewPipe to download the YT vids ahead of time. It has the option to download only the audio streams, so a lot of bandwidth can be saved that way as well.
I should note, I was not using the YouTube app, I was using the Safari browser on my iPhone all these years. To me, it seemed like a buffering problem, even at 360p. For whatever reason, Spotify loads immediately (or at worst, within five seconds) and gives me the best experience. Thanks for the tip about NewPipe.
I used NewPipe to download the YT vids ahead of time. It has the option to download only the audio streams, so a lot of bandwidth can be saved that way as well.