The result left Rovers in sixth and McCann said: “It’s two points dropped – any points lost here are dropped.”
He added: “I think it was one of the most one-sided games you’re ever likely to see.
“We had 39 shots on goal and 15 on target. We were on the front foot, especially in the second half.
“My last message to the boys before they went out for the second half was if you can’t win, don’t get beat.
“We got back to 2-2 and then for five or 10 minutes we stopped doing the stuff that got us back to 2-2.
“Credit to Paul Taylor, he redeems a mistake from one of his team-mates, and that shows the belief and character we’ve got in the changing room.”
Rovers dominated proceedings for much of the game but found themselves two goals down inside 24 minutes as Barry Fuller, with a 30-yard volley, and Tom Eaves netted with Gillingham’s first two efforts on target.
John Marquis struck from close range for his 10th of the season and Mallik Wilks headed Rovers level midway through the second half and they looked the most likely side to win it.
Max Ehmer made it 3-2 to the visitors with a volley from a corner in the 88th minute but Taylor struck back with a deflected 25-yarder in stoppage time to grab a point.
Doncaster Rovers: Marosi, Mason, Tom Anderson, Butler, Andrew, Blair (Jermaine Anderson 69), Whiteman, Kane (Crawford 52), Coppinger (Taylor 84), Marquis, Wilks. Unused substitutes: Lawlor, Beestin, May, Horton.
Gillingham: Holy, O’Neill (Nasseri 74), Ehmer, Zakuani, Fuller, Lacey (Bingham 57), Byrne, Reilly, Stevenson (Ogilvie 56), Eaves, Parker. Unused substitutes: Garmston, List, Rees, Hadler.
Referee: G Salisbury (Lancashire).