I have never dug into low level things like cpu architectures etc. and decided to give it a try when I learned about cpu.land.
I already was aware of the existence of user and kernel mode but while I was reading site it came to me that “I still can harm my system with userland programs so what does it mean to switch user mode for almost everything other than kernel and drivers?” also we still can do many things with syscalls, what is that stopping us(assuming we want to harm system of course) from damaging our system.
[edit1]: grammar mistakes
Yes, which is literally what OP is asking about. They mention system calls, and are asking, if a userland program can do dangerous thing using system calls, why is there a divide between user and kernel. “Because the kernel can then check permissions of the system call” is a great answer, but “hopefully you can’t harm your computer with userland programs” is completely wrong and misguided.