Congratulations, you now understand how proof-of-stake works - and why it’s a bad underpinning of cryptocurrencies, although bad in a different way than proof of work. Destroy the environment or make the rich richer; pick your poison.
I've personally used cryptocurrencies to bypass expensive international bank transfer fees when moving money between family members in different countries. To me, they had beneficial value for this. I'm not saying that's enough to warrant their existence, but saying they literally have no value whatsoever is clearly not true. So the question is whether they provide enough value, compared to startups. In my opinion, a lot of silicon valley startups in many industries (social media and advertising being big ones) also don't provide anything worthwhile to the world, so at least those are about on par with cryptocurrencies.
To me, investing in those startups is no different than investing in cryptocurrencies in the sense that they are equally negative forces on the world.