The largest hindrance to current Windows 10 users upgrading to Windows 11 is the requirement for "TPM 2.0" (aka "Trusted Platform Module 2.0). Many older PCs that run Win 10 are not able to install Win 11 because the installer checks for this capability, and that it's enabled, if present. I'm running a 2013 desktop with Win 10 and there's no TPM present, not even the older TPM 1.2.
There are so-called workarounds designed to let you add registry keys during the Win 11 install via a command prompt, but some who have tried them have found they still limit the install experience.
Article on how to bypass the Win 11 installer's testing for TPM 2.0:
How to bypass TPM 2.0 requirement during Win 11 installation