IMHO there should be two advantages to crafting that make it viable:

1. Cost - items obtained through crafting are more affordable than purchasing the same item from a shop. The components used to craft an item are, in total, less than the cost of the final product.
2. Exclusivity - for the most part, you can obtain any item from a shop or random loot drop that you could from crafting, but a few select items can only be obtained via crafting. Although the components might be found in a shop, dropped by a mob, or randomly found in a treasure chest, the item itself never will be.

Oh dear! I didn't realize my content needed a license until I read the Game Ideas document: All that Cat-bat stuff is OGA-BY. I'll submit something more formal as well, but in the meantime please proceed knowing it is officially licensed OGA-BY.

"...it'd be like having tags on all articles in the supermarket but not the prices, then tell users they have to go look for the prices themselves by using the tag on some big database machine,.."

What I'm saying: "This is a sucky supermarket. We should put the pricetags on this stuff."
What it sounded like you were saying: "This is a sucky supermarket. People should just steal this stuff."
I was just trying to say that a difficult supermarket experience is not an excuse to break the law. Making the law easier to follow is the solution. Letting people break the law is not. I get that you aren't suggesting people shouldn't give credit... But what are you suggesting? What do you recommend to help solve the problems you're outlining?

"2. Your game is only allowed to contain art assets from OpenGameArt.org, or made by yourself or your friends and/or associates. Using commercial assets that you not have the rights to use is not permitted."

This implies I cannot use assets that are not yet on OGA and that I did not create, but are never-the-less eligible to be submitted to OGA. For example if I found some cc0 assets by another artist on deviantart. The assets are not on OGA, but they could be. Yet they were not created by me or my friends or associates since I do not personally know the deviantart artist. I could not use these assets in the Jam. Is this the correct intent of the rule?

I think this could possibly be joined together with rule #3.
suggested omissions in strikethrough
suggested additions in bold
explanatory notes in italics

3. All newly created art assets used in your game must either already be on OpenGameArt.org or be made available on OpenGameArt.org before or at the end of the jam, provided they fit into any of the art submission categories there. <--I'm not sure this part is necessary. The categories should enforce themselves. This means if you didn't find the assets on OpenGameArt.org, you must have permission to submit them under one of OpenGameArt.org's licenses <--this should make rule #2 unnecessary. Using commercial assets that you do not have the rights to use is not permitted. <--copied from rule #2, because its an important clarification Exceptions are given for game logos, cover arts, banners and other promotional material (but if you want to post them on OGA anyway, no problem ;-)). eh, most logos and promotional art is too specific to be used by any other game, so such assets usually go against the "must be usable by others" rule. I don't recommend people uploading those assets, even if they want to.