"people earned their salary" and "learned something" aren't great arguments.
Building a bridge that collapses minutes after construction also entails workers earning salaries, and perhaps learning something. that still doesn't mean it's a good use of funds, it's waste. you want the investment to create actual value for someone.
People have tendency to abandon this line argumentation immediately when it's applied to something they admire and have been hyped up. Wasted money was actually R&D.
Example that gets almost everyone: Space Shuttle.
It was supposed to be reusable space truck that reduces cost. It was several times more expensive than conventional approach with non-reusable rockets and shuttle. It was infrequently used. It drained NASA budged from anything productive. Even those combined manned+cargo missions could have been achieved cheaper with double launch. It was objectively failure based on the goals and purpose of the project.
They developed so much new technology and inspired people. It was simply great piece of engineering and PR. We learned a lot.
That being said, I believe the SLS gave many more spin-offs than the Magic Leap
I wonder if there were missions that would not be possible without it (maybe the Hubble launch and the AMS launch and installation) though most likely they would be adapted to work without it.
Another way to say this is that VCs could just have donated money without spending 8 years spinning the wheels. Those employees would have been paid and the opportunity cost of spinning wheels would have not occurred, instead these people would be doing something more productive and adding value to the GDP.
So, I agree with you. It is a waste. It is a waste of human hours that was spent with nothing to show in return.
Building a bridge that collapses minutes after construction also entails workers earning salaries, and perhaps learning something. that still doesn't mean it's a good use of funds, it's waste. you want the investment to create actual value for someone.