Anyone can act totally deadpan and extremely brilliant in their own consecutive movies. Depends largely on the script, how the director handles the talent or even how interested the artist is in doing that role just to name a few reasons. It may be art to some but the reality is it's a job. Some you like so you do it wholeheartedly and some you do just for the money. I'm pretty sure she can act if she gets a role that she loves. You said mahanati is recent.it had some good acting from her part but It was four years ago. Just watch saani kaayidham. That is one of her recent movies. The script demanded excellent acting skills and I think she fulfilled it brilliantly. But most films. Another example is kalidas jayaram. That guy can be absolutely brilliant in one movie and act totally brain-dead in the very next. Don't ever rate one guys acting skills in a movie based on his performance in another one.