I haven't seen it used even once. There were plenty of opportunities too to show case it. Guess Kishi decided to just do away with that and focus solely on the MS techs?
how many uchiha's are there to begin with. .itachi, obito n sasuke. .itachi died. .and as for sasuke n obito they need not copy any jutsu . .they already hav best possible counter attacks
Handseal are not even used that much; current sharingan users can slice mountains and produce broken flames; tracing, copying and adapting some moves are not even that needed at such power scales.
MS, EMS and Rinnegan said no to that. Most of the things we have seen in Shippuden is kekkei genkai that can't be copied, anyways. All of akatsuki had techniques Kakashi, Obito, Sasuke or Itachi couldn't copy.