I have had the opposite experience. I've found windows defender to be basically the only AV you really need. I had a single occurrence where it flagged software I was writing as potentially malicious, but I was able to add an exception for my project and not think about it again. I've never noticed it clocking my CPU at any noticeable levels. For comparison, my work computer requires McAfee and at least once a day it clocks my CPU at 65% or more.