For most OSes the amount of code that actually deals in processor minutiae is really quite small. Portable logic makes up the majority. Maybe an exception can be drawn for some very particular OSes like DOS or Windows 9x.

So you read a tutorial and it spends about 90% of its time talking about an area that really isn't that interesting compared to other areas. I just don't think that's very compelling at all.

I say this having my own hobby OS which I've ported to four architectures (m68k, amd64, aarch64, riscv). At the moment I'm working on a TCP/IP stack which has been really enjoyable and I've learnt a great deal in doing this already. Other fun areas have been virtual memory and page replacement, designing asychronous I/O facilities, and IPC mechanisms, as well as appropriate synchronisation for each (synchronisation alone is a very deep topic, and there's considerable scope for innovation with techniques like safe memory reclamation.) Others may differ, but in these I find a lot more of interest than x86 minutiae.