What we learned directly from the human genome is precisely that - the structure and sequence of the human genome. What that enabled (directly) is the ability to understand what genetic material is there that can govern all of the complicated biochemistry going on in the body.

More importantly, in sequencing a large genome like that of humans (nowhere near the largest, but pretty big compared to what was sequenced prior to that) is that we gained the technology (which has since become orders of magnitude better) to sequence more genomes. From this we can compare genomes of humans and other animals to help understand what makes our biology different (or similar) and also other humans to help understand what makes the biology of some humans different from others.

The genome was sequenced only about 20 years ago, but pretty much any medical advancement happening today uses that knowledge of an accurate genomic sequence somewhere in development.

The best analogy may be the invention of a transistor. At the time of the invention, 75 years ago, the basic understanding of electronics was there, and it performed a function that was not too dissimilar from vacuum tubes that existed already. However, the use of the transistor, combined with other inventions such as integrated circuits, photolithography, and many many more ended up revolutionizing the approach to electronics and the speed of their development. In this sense, having an accurate genetic sequence and being able to sequence human cells, combined with other developments has revolutionized our approach to molecular biology and medicine and is a very important building block. Hence why it's regarded as a big achievement.