There must have been some golden era with 20000 runners and no crowds...
I only have this year's marathon, mid to back of pack experience to speak from, but it's par for the course for most major running events.
it even felt sparse around mile 22.
Far Far Far better than say, Bay to breakers, in it's heyday with people wheeling kegs and DJ floats down the middle of the street at a walking pace. (or salmon running the course in reverse). 7 miles of wall to wall participants (runners?)
I also ran a half marathon across the golden gate bridge where the outbound runners were confined to the sidewalk (2-3 wide) and the return runners were confined to a single lane of traffic, I didn't get passed or pass anyone for 3 miles.
Suffice to say, I've run much worse. was it perfect? no, but there's no completely naked guys in my finish photo... (my third bay to breakers I learned to just let them pass me at they wouldn't be in my photos).
I wish it were on a more convenient weekend for me