PDF is not meant to be edited, it’s meant to be a digital representation of physical paper.
The other problems are just people who don’t actually learn to use Microsoft Word, you certainly can add more words to spellcheck and you can change how images and text interact, the only thing I can think of that caused issues is at one point they changed the default, too many people never learned how to change the layout and keep expecting the old behavior after the change.
Because there’s no finance bros investing in them. Pure supply and demand baby.