The biggest concern right now is the looming massive unemployment crisis and you’re worried about too much demand for work?

It's a two sided issue. We're laying off a bunch of people in jobs that require thinking, but not doing stuff in the physical world. But jobs that require doing physical things are still much more difficult to automate if it requires any sort of flexibility to conditions. We'll still need people in a bunch of roles, they'll just be jobs people won't want to do as much, because it'll be dirtier and harder work. And of course in our present economic system at present time, these jobs aren't very highly paid since we don't have a real shortage of workers yet.

And how does fewer working people decrease resources? Fewer working peole means less land? Less water? Less energy?

Land on its own doesn't produce much useful, you still need people to work it. Power plants need employees too. Etc. There are still so, so many things we can't accomplish without humans physically present and moving objects. Automation makes things more efficient, but we still need humans.

If the population of the world shrunk evenly in all ages, it wouldn't be an issue. It's only an issue because the population is aging.

And yes, in the future we'll probably have AI doctors, AI teachers and AI engineers to provide us mediocre healthcare, education and help invent stuff. But we won't have AI electricians or AI plumbers anytime soon. Much harder problems to automate.