Subpar is really stretching it. With some care, Flash content could behave quite well on the iPhone. It was not 100% proprietary. Of course it wasn’t 100% open either, but then I direct your attention to the Apple App Store.
Edit: Flash Paper was hot garbage. Definitely not going to defend that one lol
It came out years later that Apple hired Adobe to help, if Adobe couldn't do it, I don't blame Apple for abandoning it. Looking at how difficult it is to build an open implementation of Flash via Ruffle, I don't think subpar is a stretch.
Subpar was accurate. What you can theoretically do with an SWF file given a new from-scratch runtime and what you could actually do with the extant Flash player at the time are different topics.
Edit: Flash Paper was hot garbage. Definitely not going to defend that one lol