"Our bowlers have done well but we have struggled to find the right batting combination," McGrath was quoted as saying in Tuesday's The Hindu newspaper. "We have changed a few things around this last Test, so hopefully we will improve but Australia has been well and truly beaten."
Australia frequently changed its top order throughout the five-match series that ended on Sunday, with Chris Rogers, David Warner and Shane Watson opening at different points of the series. Watson, Ed Cowan and Usman Khwaja were all tried at number three.
McGrath, the most successful fast bowler in Test cricket with 563 wickets in 124 matches, also said pace bowlers are increasingly facing injury as there was no respite from competitive games.
"I have trained so much harder in the off seasons than anything I did in the middle. I played 55 Test matches in a row without missing one. The guys who are getting injured all the time....there are little inefficiencies - like a mixed action - or they are not physically fit or strong enough.
"That comes with age as well as work ethic. It's in the mid-to-late 20s that a fast bowler begins to mature," McGrath told journalists on Monday on the sidelines of a camp he is overseeing at the Madras Rubber Factory pace academy in the southern city of Chennai.
McGrath also said his opinion of the Decision Review System had changed during the Ashes, as the system of referrals to the television umpire regularly came under scrutiny.
the start of the Ashes, I was a big fan of the DRS. The more I have
seen it I can see why India doesn't like it. I have lost a bit of faith
in it," McGrath said.