Rare earth metals are mostly not rare. The vast majority of rare earths are plentiful. We're not going to run out of the most useful rare earths for hundreds of years at a minimum. It's the extraction and processing that is a problem (environmentally), not the scarcity factor. The US for example is loaded with rare earths and has barely even scratched the surface of its supply (the same is true of Canada and Australia); there has been a lack of interest in rare earth mining in the US for the past several decades because of how intense and dirty the process of extraction and processing is.
> The rare earths are a relatively abundant group of 17 elements composed of scandium, yttrium, and the lanthanides. The elements range in crustal abundance from cerium, the 25th most abundant element of the 78 common elements in the Earth's crust at 60 parts per million, to thulium and lutetium, the least abundant rare-earth elements at about 0.5 part per million.
https://www.usgs.gov/centers/nmic/rare-earths-statistics-and...
> The "rare" in the name of this group of elements is actually somewhat misleading; the U.S. Geological Survey describes them as "relatively abundant in the Earth's crust."
https://www.scientificamerican.com/article/dont-panic-about-...
https://www.smithsonianmag.com/science-nature/rare-earth-ele...