The French international, who has been recently linked with a move away from the Santiago Bernabeu, netted the winner as Madrid beat Granada 1-0 on Monday night.
While he was happy with Benzema's display, Ancelotti feels that his teammates need to improve heading into their next match.
"Karim is playing well, scoring and working hard. He's started La Liga well," Ancelotti told Real's official website. "I think we attacked a lot but we didn't finish off those chances, which we need to do.
"The start of the game was good, but then our pace dropped. [We're] working to improve. We are trying to change the team's philosophy and at the moment the important thing is to win points.
"The first half was good and all we needed to do was score the second goal, but 0-1 is not easy to control and experiencing some difficulty is normal. Now what's important is the result. The team was compact and they all played well and made an effort, so I'm happy."
Madrid host Athletic Bilbao in their next match on Sunday.