There are plenty of reasons to criticize Microsoft but I don’t think this is one of them. First, Windows Defender is quite good as far as antivirus software goes. If you ever had to do desktop support in the days when Norton, McAfee, and AVG reigned supreme, then you know what I’m talking about.
Second, one of the biggest challenges for an OS vendor is backwards compatibility. Especially since Windows dominates the enterprise space and has for the last 25+ years. Big corporations can get really cranky about their legacy applications from 1998 that are still basically holding the entire org together. While it’s short sighted to not be proactive about keeping your technology current, it’s also a reality that many businesses simply aren’t proactive.
Windows definitely has its flaws but it has come a long way in terms of both security and reliability over the years.