There are no complete sets, just loose bricks and a few instructions.

Sets is just one mindset. There are people with a different mindset who do want unsorted bricks. I do realize you were replying to a specific mention of sets though.

I've looked into it a bit. With some exceptions for very rare pieces, it's almost certainly not worth the effort of cataloging all your random LEGO pieces, unless you enjoy the process itself.

Spread it out onto the floor, photograph it, and stick it on eBay for $20 or whatever.

Or, donate it to a school or charity shop (thrift store?).

That you don't want to realise the full value doesn't mean it has no value.

Agreed, that's not worth it if you value your time. But a rough idea of what sets are in there plus a kg price and someone will be happy to take it.

Right, though I said nothing about cataloging.