As I understand it, superconductors work best at temperatures approaching absolute zero (-273.15C). For example, Google tells me that the superconductor in an MRI operates at -269C.
There has been a lot a buzz lately about room temperature (25C) superconductors being discovered, but why is room temperature the focus? Why not focus on superconductors that work in reasonably cold environments? For example, we can easily get temperatures to -15C in a freezer. Why not create superconductors that work in that temperature range rather than 25C?
It’s not a video game tech tree. Scientific progress isn’t linear. We hypothesise, we experiment, and sometimes we get lucky. If it was an engineering problem we could make incremental improvements to the manufacturing process to get small improvements in the results, but it’s not.