If they were spending the money on those things, this might be an argument. But they're not spending it; they're hoarding it.
The point of an endowment is to provide long term support for whatever the purpose is of that endowment. That is done by investing it and using the investment earnings for that purpose.
There is something ironic about people who work in start-ups arguing for endowments to be spent down. Who do you think gives money to the VC funds?
1- https://projects.propublica.org/nonprofits/organizations/231...
UPenn’s revenue includes “sales of assets” and “investment income,” i.e., taking some part of the endowment annually to fund their operations.
It's not a pile of gold sitting in a vault on campus. It's an account which is productively invested and generating returns which are what's actually used for funding operations. A $20 billion endowment would be expected to produce about $1 billion per year, or around 20% of the annual operating budget. They need to bring in about $4 Billion more dollars per year to keep the lights on.