CERN wants to build a new collider, and inevitably people will say that we should use the money for something more useful.
There is nothing more useful than what CERN does.
If we're going to have a long-term future as a civilisation ('long-term' being more than a human lifetime ahead), we need two critical bits of technology (we need others, but we need these two).
The first is really good batteries. Well, you carry around with you a machine which pretends to be a communication device but is in real life part of a large-scale test and development effort into good batteries. It's unfortunate that this effort is having bad side-effects: social media and the awful consequences of it, such as Trump, Bolsonaro, Cummings-Johnson & all the other cartoon characters who have leaked into the world from various dystopias and are busily burning our future. But battery development is proceeding well.
The second is, unfortunately, something you can't fool people into testing in bulk for you, because it's not very domestic: large-scale superconducting power systems. You need these because you are going to need to ship enough electrical power to run half the world half way around the world, from where the power is made to where it's needed, and you're not doing that unless you have really enormous, really reliable, superconducting power networks.
Well, that's what CERN is: it's a huge test and development environment for production superconducting power systems: by far the biggest in the world. Yes, there's some interesting particle physics strapped onto the side of it, but that's not what it's for: what its for is the development of really large-scale, production superconducting power systems and the people who understand how to build and run them.
What CERN does is give us the hope of a future. That is unfortunately not something you can sacrifice, unless you don't want a future.