I'm not an expert, but as I understand it there isn't a complete theory about why high-temperature superconductors work, so inventing new HTS types is sort of a matter of just trying different materials and hoping you get lucky. If this new research fills in some important gaps then it might make it much easier to discover better materials.
These would have some practical applications. Cheaper MRI machines. Long-distance lossless power transmission. Tokomak-style nuclear fusion reactors use superconductors to maintain magnetic confinement, so better HTS materials mean better magnets, which means a more efficient reactor that doesn't have to be quite so big. (The MIT Sparc reactor design uses ReBCO tape.)
These would have some practical applications. Cheaper MRI machines. Long-distance lossless power transmission. Tokomak-style nuclear fusion reactors use superconductors to maintain magnetic confinement, so better HTS materials mean better magnets, which means a more efficient reactor that doesn't have to be quite so big. (The MIT Sparc reactor design uses ReBCO tape.)