Funding research, and what research to fund is a big topic.
Your BiL has a point. When the energy and water run out, there will be wars like you can’t imagine. It’s a practical problem. It feels solvable too.
But space exploration is needed to answer important philosophical problems about life/identity and the nature of the universe/existence. To a lot of people, this matters somewhat less.
Nothing matters more to the masses than Sky sports, mind you!