It was about cobalt before, now that batteries switched to LFP without cobalt the naysayers switched to complaining about lack of lithium :)

I'll note that neodymium is, and is used in very small amounts (much less even than lithium) in most EV electric motors (specifically, the reluctance types that are currently most popular). It's not essential, but it does increase range by a few percent.

Neodymium is also one of the most abundant REEs- there are basically two groups of REEs, some of which are rare and some of which are >10x more abundant. Neodymium is in the latter. It's also not that supply is restricted (eg, how it all comes from china)- the demand is so low that the cost means it is not mined even where it is easy to harvest. There are large mines in the US and elsewhere that are shut down because China just does it cheaper.