we have this conversation all the time and it's so overwrought.
a good prospect carries some inherent value, but his real value is determined by either what production he provides you, or what someone is willing to give you for him. every single guy in the minors is, at the end of the day, measured in opportunity cost. can he help the team today? Might he in the future? Might we get something for him today in a trade in exchange for someone betting on his future?
it's easy to go "we don't need all these OF prospects" or whatever, but if your options are call them up but they don't play, leave them in the minors, or trade them for less than you value them either now or potentially in the future, there's risk with every option. It's not "prospect hoarding" to leave a mid-tier OF prospect in AAA because you can't find a valid trade partner and he's not ready for the majors. It's value hoarding. And there's a risk that the prospect stagnates and loses all value and you get nothing out of him. But that's not inherently more risky than trading him for less than you value him just because he's blocked.