"It honestly feels like 80%+ of the card pool are either useless or actively detrimental to your ability to win."
I had the same initial impression but gradually more of the card pool opened up to me.
My picks for "Trash tier"
either Quartz
Ore that costs energy / wants lots of buffs
(Quartz Ore is my pick for single worst card)
Treasure Map
Wrench
Corkscrew
(edit: updated to reflect further understanding)
Everything else I think is fine (or at least interesting to make work & feels good when you get there)
I think you'll find a wider range of cards than you realized are good for Prospect grinding (especially +Energy, buff targets & enablers), and many of the others can be built into viable decks that are not mostly about Prospect grinding.