Scientifically this is absolutely a breakthrough, just like the detection of the Higgs boson was despite them already having expected it or just like LIGO's detections of gravitational waves were despite that being entirely what it was built for or just as JWST's detections of galaxies much older than those seen from other telescopes was despite that being part of the entire point of dumping billions into it. Ingenuity's first flight was also hailed as a breakthrough despite that being exactly what it was designed to do.
In every case we had an idea of how to solve a problem and the outcome was generally expected. All that had changed was that the data had been collected of the solution working, just as it has been in this case.
To put it differently, it's a breakthrough because after decades of work, the National Ignition Facility can actually achieve the thing in its name.