Able to compete for three quarters against the Brisbane Lions at Etihad Stadium, the Dogs conceded 7.5 in the second quarter, setting them on the path to a morale-sapping eight-point loss.
It was the eighth time this season they have conceded six goals or more in a quarter, with McCartney pointing out the trend in his post-match press conference.
"The development that hasn't taken place is to be able to deal with [and] not let a horror five minutes become a horror 25 minutes," he said.
"In the end we weren't good enough for 40 minutes tonight and we're going to accept responsibility for that … I take responsibility for it.
"We're disappointed in how we played tonight, we're disappointed as a footy club.
"It was a similar tale to most weeks unfortunately for us."
RECAP: Match report and match highlights from the Western Bulldogs and Brisbane Lions clash.
McCartney said his team lost Saturday night's match in the second quarter and through "our refusal to kick the ball forward in the last quarter when we had our hands around their throat".
Indeed, the Bulldogs kicked four of the last five goals in the final term, with Adam Cooney's clutch set shot cutting the margin to just 17 points after 15 minutes.
"I could see us getting more dangerous and responding, getting a better reward for our work," McCartney said.
"Then I saw us invite them back into the game by not wanting to go forward with the ball and kick it, which kept them in the contest.
"There were periods in the game tonight where all areas of our game weren't up to scratch.
"Because of that as a football club we've missed a great opportunity to take another step forward."
McCartney highlighted the Bulldogs' inability to compete at the coalface during the second quarter, with the Lions controlling the match through contested ball.
PHOTO GALLERY: View the Bulldogs and Lions match-up through the lens of AFL Photos photographers.
"They slaughtered us in that area," he said.
"For about a 40-minute patch we got a real pantsing in that area … very few people were up for the fight in that patch.
"One thing I said to the boys after the game, I'm in it with them. I'm the leader, the leader goes first.
"You take the criticism, you take the feedback, you deal with it, you don't wallow in your pity and you turn up for work on Monday, because there's another opposition waiting next week."
The Bulldogs will be chasing their fourth win of the season against Collingwood at Etihad Stadium next Sunday.
