To be fair, we did get a very good mirror fight, it just didn't feature Taskmaster. The fight between Natasha and Yelena in Budapest was very well done.Just saw it and I really liked it. Of course it was much lower powered than what we've become use to in the MCU but it fit as a Spy movie. I'd rate it better than the Ironman movies and better than Age of Ultron.
Talking about spy movies I thought the villain here worked well for a spy movie, the scheme was very Bond-like and suitably vile.
Yelena (Florence Pugh) was the best character and the movie really was a hand over to the new 'Black Widow". The relationship between the sisters was great and I would have focussed on that more (and dropped the parents). It might have worked better as a series rather than a movie.
I agree that Task Master was criminally underused, the photographic reflexes werent really explored and we didnt get a cool mirror fight, in fact there werent any very good fights in the whole movie.
the best part of the movie though was OT Fagbenle, I cant wait to see him back again in Thunderbolts or Dark Avengers