why my pc is not eligible for windows 11?

Microsoft has strict hardware requirements for Windows 11, especially the need to support certain security features, such as TPM 2.0.

A simpler solution is to use a tool like WinnBootMate, which can help you create a bootable USB that meets the requirements and bypass some hardware checks. I followed this tutorial and it worked:

https://www.smartpcguide.com/windows-11-requirements-bypass

However, I do not recommend modifying the registry to force the upgrade, as doing so may cause system instability or other security issues. You still have to consider whether it is really necessary to upgrade, or you may need to consider upgrading your hardware.