Does Windows 11 core isolation protect me against malware or does it have nothing to do with it? For example, an unsophisticated hacker with metasploit, nmap, msvenom or tools like that could create obfuscated malware or code that can run on a PC with the isolated core and RAM or that type of code. Or does malware for reverse shells not need to access those protected parts of the system?
You have a few things confused together. It is possible to create malware that includes a reverse shell that does not require "hacking" the system.
Core isolation helps to isolate high-security parts of Windows memory to prevent abuse and misuse of memory to gain privilege isolation. So, from this perspective, core isolation helps prevent certain ways of gaining access to the system through exploiting other programs.
As with all things in security, there is no single, simple, conclusive solution to complex problems.