Awesome to hear of new people getting into PCBs! It's wonderful how accessible PCB design has become, and I think KiCad plays a major role in that. If you're the kind of person who can read to learn stuff, I highly recommend this old powerpoint presentation:

https://www.4pcb.com/media/presentation-how-to-build-pcb.pdf

It describes the manufacturing process in pretty good detail. The reason the design rules feel like such a wall is that these design rules are completely based upon the manufacturing processes themselves (thus different manufacturers will have different rules). As you go through that presentation, you'll probably have to search or ask about many of the terms you don't recognize, but that'll just help you learn even more! Next, check out the design rules for a popular fabricator. For example, here's one:

https://docs.oshpark.com/services/two-layer/

And they even include some helpful tips for setting up KiCad to work with their fab capabilities:

https://docs.oshpark.com/design-tools/kicad/

Two other great resources to learn from are Robert Feranec and the Contextual Electronics course: https://www.youtube.com/@RobertFeranec https://contextualelectronics.com/

Have fun!