Your 12 years old pentium 4 (or whatever) likely has 1 core and 1 thread, which is immensely noticeable even compared to the lower end modern 2 cores/4 threads

Your 12 years old pentium 4 (or whatever) likely has 1 core and 1 thread, which is immensely noticeable even compared to the lower end modern 2 cores/4 threads machines (let alone 4/8 mid level modern desktops).