It means we won't lose MRIs when the earth finally runs out of helium as they require liquid helium to run the superconductors that generate the magnetic field. We're running out of helium with no way to replenish it. Helium is the only element on the periodic table which is a non-renewable resource on Earth.
So MRIs will get much cheaper, and they could end up being as cheap as taking an x-ray today.
Based on our current data LK99 isn't a replacement for helium cooled superconductors for the same reason YBCO and similar aren't - critical current/critical magnetic field aren't in the right ranges for what we need out of MRI machines.
I do think it's too early to say one way or the other what all of this ends up looking like, so we might find that purer/larger samples have better properties than what was measured so far, or the discovery puts us on the trail of other RTAPS in the same class that might be better for these purposes.
I never claimed LK99 had the properties needed for MRIs, the question I was answering was "how will the world change with room temperature superconductors", and my answer is valid in the context of the question.
If the earth runs out of helium we will just use low field MRIs that don't require superconductors (see eg https://www.nature.com/articles/s41467-021-25441-6 ). Their resolution is lower than that of high field MRIs, but they still seem to be a useful diagnostic tool.
I suppose you could count elements like gold, too. Since we technically can produce extremely radioactive gold in small amounts but the cost is so prohibitive it would never make sense to.
In a thousand years people are gonna look back at us idiots filling balloons with helium and letting them disperse into the upper atmosphere and shake their heads at how stupid we were.
So MRIs will get much cheaper, and they could end up being as cheap as taking an x-ray today.