Then you have dumb stuff like if you check a box and want some additional form fields, you have to inject a div or input into the DOM manually, and then make sure you initialize your datepicker, but maybe there will be a flash of unpickerified input if you don't do it right.

I haven’t used jquery in 10 years or so, but I’m pretty sure this isn’t what you would do. You would just hide or unhide the inputs with jquery.

That is true, but this is built-in to React and it's optional for JQuery. I am working on legacy projects a lot and nobody ever writes JQuery like this outside of famous libraries.