Accessibility(a11y) is HARD. One person’s a11y, is not another person’s, and they can conflict sometimes. I don’t know of a conflict with your particular example of having a send button, instead of only the enter key sending, but I’ve come across cases that have.
For example, some deaf people have ASL as their native language, and english skills are not very good, so even using a computer can be difficult, since there is (currently) no way to have anything approaching a native language interface for ASL native signers. There still is no paradigm of computing that is 100% visual, and could be done with ASL. Yes, I’m aware of the ML work around having computers “learn” ASL, but let’s face it, computers can barely handle very simple english(see Siri, Alexa, etc) and there is way more resources dedicated to that.
Also, I use ASL here merely as an example, most countries/geographic areas have their own local signed languages, independent of their native spoken/written language.
a11y is not a check all these check boxes and you are magically perfect, There are general things that help, just like in PwD’s physical world(s); Mobility enhancements tend to be fairly unique for an individual person as an example.