You are likely on a newer version of macOS (Sonoma or later). You cannot “downgrade” via Software Update. You must create a bootable USB and clean install.
Thus, while downloading Ventura 13.2.1 today is fine for offline machines, legacy software, or secondary Macs, unless you have third-party security software (like Little Snitch or Intego) and practice strict browsing hygiene. Ventura 13.2.1 Download