Oh it's not just me?
Typing on my iPhone in the last few months (~6 months?) has been absolutely atrocious. I've tried disabling/enabling every combination of keyboard setting I can thinkj of, but the predictive text just randomly breaks or it just gives up and stops correcting anything at all.
It’s not just you, and it got bad on my work iPhone at the same time so I know it’s not failing hardware or some customization since I keep that quite vanilla.
I haven't watched the video, but clearly there's a broad problem with the iOS keyboard recently.
https://news.ycombinator.com/item?id=46232528 ("iPhone Typos? It's Not Just You - The iOS Keyboard is Broken")