Win 11 on a pre-8th gen CPU even with TPM 2.0 can work if you do this or bypass install checks other ways, but you lose some security features: older CPUs lack hardware support for VBS (Virtualization-Based Security), HVCI/Memory Integrity, Mode-Based Execution Control (MBEC), which Win11 may expect to be enabled and rely on more in future, and newer exploit mitigations which can make the system less secure.
You may also face blocked feature updates in the future, no guaranteed security patches, and future driver/compatibility issues since your hardware isn't validated for Windows 11.
I mean go nuts, do it, but that's the downside.