That's just terrible.

Alas, I think you're almost certainly out of luck, since the mileage credit between *A partner airlines involves some pretty hefty payments back and forth each quarter. From the measly looks of that chart -- 25% miles for the cheapest economy seats?! -- it looks as if LOT just isn't willing to pay what other airlines do.
Turkish, for example, credits 100% mileage toward UA even in its cheapest economy seats:
https://www.united.com/CMS/en-US/Mar...spx?ItemId=306