neowin[.]net/news/windows-11-23h2-upgrade-causing-performance-loss-and-trusty-microsoft-defender-may-be-why/
Gamers are reporting a decrease in performance after updating to 23H2 -- it likely effects more than just gamers, but the average non-gamer isn't keeping track of CPU, GPU, & fps in a sort of continuous benchmarking process.
A Microsoft rep told one person to reset Defender, but then went on to include turning on the VBS security feature. This person did both, and reported performance was restored. Because they did both however, can't say whether resetting Defender worked, or if a change to Defender means it works better with VBS on rather than off. IF you are experiencing reduced performance, guess all you can do for now is try just the Defender reset and see what happens.
Received an answer from Microsoft after 3 days, they told me to reset Windows Defender through a couple of PowerShell commands(1- "Set-ExecutionPolicy Unrestricted" and
2- "Get-AppxPackage Microsoft.SecHealthUI -AllUsers | Reset-AppxPackage") then reboot and enable CPU Virtualization in BIOS (SVM in my X570 BIOS),