Not sure if I’m missing something about this method, but in many apps you can long-press the word directly to get the context menu with “Look Up”, without having to type the word into a note.
The use case here is to look up a word whilst reading a book, not to look up words that are already on your phone screen. If you see a word you don't recognise, you write it into a note and it gives you the definition instantly
Pro-tip: Now you could also use iOS' camera app to recognize the text, select it and look it up. I'm not sure if it's faster than the note route but the option is there.