No; that's just you picking an absurd example rather than being practical.

Pick a reasonable domain for each input field, considering what kind of input is useful, and what kind of usage in output (i.e. plain text output is likely much less risky than rich text). There's rarely a reason to ban < in plain text; but retaining stuff like zero-width joiners or rtl-ltr-transitions is likely less valueable, and potentially an issue with in things like usernames or email addresses (because they make it trivial to make apparently identical usernames). Similarly, if you're storing a telephone number and want to retain spaces - are you going to retain nul-chars too?

Not all input should allow arbritrary plain text. I'd guess most don't, and lot's of input is at least rich text nowadays (not to mention images and other media - you think it's a good idea to just reproduce an arbitrary image exactly?).