Why would he be now? This isn't about some perceived weak era anymore. It's about Djokovic looking like he'd rather be anywhere but on a tennis court. It's about him losing to Denis Istomin at his favourite tournament. Losing to Wawrinka in the USO Final (after getting a cakewalk of a draw to get there), and losing to Sam Querrey at Wimbledon. In between have been losses to RBA, Cilic, Delpo, and Murray, along with a withdrawal from Cincy.
Could he get his form back? Absolutely, and I'm expecting him to do so at some point (although not to his 2015-mid 2016 levels), but he's not a huge favourite in every tournament he plays anymore and I suspect he may never be again.
Father Time never loses.