Okay, I think I have the basic process understood. Lymph gathers up all the crud, gets carried back to the nodes by the lymphatics, and there filtered out of the system. The raw lymph then gets put back into the blood and so back into the cycle. But what happens to the stuff filtered out by the lymph nodes? Does it get dumped into the blood as well, to be cleaned out by the kidneys or something? Or is there another system for getting rid of it?
And feel free to correct any of the preceding assumptions. Thanks in advance.
If blood vessels represented interstates, lymphatics would be closer to local roads. They are the bodies’ transit system for materials that don’t need to get there in a hurry.
I can think of three major functions for lymphatics. First, they link the skin and internal organs to a major component of the immune system, the lymph nodes. Second, they comprise the conduit allowing excess fluids to drain from tissues back into blood vessels. Third, fat is transported from the gut to the blood stream (and then the rest of the body) via lymphatics.
I don’t think of lymphatics as sucking up much crud, though. They conduct lipid, fluids and immune cells to lymph nodes and the central vasculature. Vital functions like nutrient transit and immunity are subserved. Pal, this ain’t crud removal. 
Removal of the byproducts of metabolism (CO2, lactic acid, ammonia, etc) is left to the blood circulation. The reason for this is probably because our bodies take this waste removal seriously. That shit needs removal, pronto. If metabolic wastes dawdled through the lymphatics on their way to such destinations as the lungs, kidneys, and liver, our frenetic lifestyles would prove impossible.
You may find some consolation, however, in the spleen. You can conceptualize of it as a giant lymph node that sees lots of blood flow from the portal blood system. It has a central role in resistance to blood borne bacterial infections but it’s also the elephant’s graveyard for worn out red blood cells and (I think) platelets. Thus, crud collects in the spleen.