Duracell (the Mallory company) was bought by Dart in 1978, then by KKR in 1988, Gillette in 1996, Procter & Gamble bought Gillette in 2005, and Duracell was spun off and bought by Berkshire Hathaway in 2016. (source: Wikipedia)

The company has been under large-scale finance / conglomerate management for more than 4 decades by now. I don’t think there would have been any immediate change in battery quality circa 2016. Seems just as likely that corner cutting (assuming there is corner cutting; I have no insight) started before changes of ownership.