My old job included the filthy, awkward task of scraping praseodymium-containing ash out of an expensive, unreliable and scientifically dubious device called a Weather-O-Meter. Yeah, useful stuff.
As for tantalum, you better not tell Ed Anger it’s useless! It’s been used a lot for making medical implants, including plates that are implanted in people’s heads when they lose part of their skull, like Ed did in Korea.
I never had much use for strontium, myself.