Today... a typical PC mainboard schematic might be hundreds or thousands of pages
Go find one and take a look. Seriously, they're out there. Google an OEM name followed by "schematic" (quoted, because otherwise anti-repair Google will misdirect you to owner's manuals and other shit) and start reading. I'll challenge you to find one that's over 100 pages, because I personally haven't seen one. They're closer to 50-70.
A few decades ago nearly all but the most complicated devices could have their entire schematic printed in the last few pages of the owner's manual.
Today... a typical PC mainboard schematic might be hundreds or thousands of pages dealing with all sorts of complications for RF and stuff.
What would 99.999% of people do with such a schematic?