I seem to remember way back in the day that you could advertise with Slashdot (and others, I'm sure) by giving them an image (static or animated GIF) of specific dimensions, the URL that image should lead to, and obviously some cash
Right, direct advertising. IIRC, anybody who seriously suggests it is routinely shouted down as impractical.
If you hosted static ads like it sounds like they did wouldn't it then end up costing more work for less money? If you have someone else host the static ads it'll be the same amount of work but you'll get less money. The issue is that most people don't want to get less money
Well, the first problem is that only a relative few sites are big enough to do direct advertising. The harder question is how to keep web content decentralized by decentralizing means to revenue, a battle we are aggressively losing.
Right, direct advertising. IIRC, anybody who seriously suggests it is routinely shouted down as impractical.