The phrase "unattainable goal" means a target or objective that is impossible or very difficult to achieve. It refers to something that is too far or challenging to reach. Full definition
It's a dangerous game to constantly compare any siblings, but when you're trying to compare a kid with a medical condition to their sibling that doesn't, you're instantly making unattainable goals for them. (twiniversity.com)
The appropriate remedy is often seen in the, as yet, unattainable goal of a grand multilateral treaty. (newlawjournal.co.uk)
Finally, when there's greater impact at play, you're motivated to achieve big, unattainable goals because you're aware of the meaningful difference your company can make. (entrepreneur.com)