What kills it for me are the apps where you can't copy a single word. e.g. Apple's own Messages app, you're forced to copy the whole message.

Same for the spell checker. For some reason I have ridiculous trouble triggering it in certain apps. I can see the mistake underlined in red but I really struggle to get trigger the correction popup instead of the "copy, lookup, etc" popup.

Maybe it's just me but I don't think I could consider an iPad as laptop replacements without some basic changes to iPadOS.