Research indicates that it is likely because ISA Alerts rely on Win2K's Performance Logs and Alerts service, which I had previously disabled.

Microsoft says this month's Patch Tuesday cumulative updates also fix a known issue causing Windows Server 2019 boot problems, freezes, and performance issues after installing the August 2024 ...

If you face a Windows Server slow performance issue, you can upgrade the hardware, such as Memory or the Processor. More working suggestions here.

Microsoft has confirmed and fixed a known issue causing performance issues, boot problems, and freezes on Windows Server 2019 systems after installing the August 2024 security updates.