In short: Windows Defender isn’t bad, per se, it just isn’t as good as your other options. However, it’s by far the least intrusive, considering most other antivirus programs come bundled with crapware, install problematic browser extensions, and contain occasional popup ads.
If you’re following common sense and other good security practices, Windows Defender may be fine, depending on your risk tolerance. However, if you’re regularly downloading pirated applications or engaging in other high-risk behaviors, you may want to skip Windows Defender and get something that does better against the collection of obscure malware samples used to test antivirus software.