There are about a zillion ways it could prove to be impractical. Apatite is a crystal, and presumably this lead apatite is also a crystal. We also don’t know if it can be deposited in a useful thickness; the samples tested so far were created by gas deposition on glass. Can it be built up to a useful thickness, and maintain its superconducting properties? All unknown.
But, real progress always comes in small steps. It’s exceedingly rare for any discovery to result in a useful product immediately.
Sure… but for every 1 of those examples, there are 100 or 1000 variants that showed astonishing properties in the laboratory that were never manufactured at scale due to cost or other undesirable material characteristics.
Lead apatite may turn out to be an important step, or maybe not. When Paul Chu made the first big breakthrough with yttrium/barium superconductors at liquid nitrogen temps, everybody thought that workable room temperature superconductors were right around the corner. That was almost 40 years ago. As of right now, we don’t know whether “room temperature superconductivity at scale” is 1 year or 1 century away. It’s closer, probably? That’s about all we can guess.