In recent months, the YouTube Music website/Progressive Web App (PWA) has seen a number of updates that combine to really overhaul the desktop experience and make it more competitive.
In March, music.youtube.com gained the ability to download songs. Previously, the only path for offline playback on desktop (just ChromeOS) was using the Android application.
With the PWA adding offline support, Mac and Windows finally have this basic music app capability that is helpful when traveling, like on planes. This functionality was a big reason why people wanted a native desktop client. I don’t think Google is ever going to build that given the philosophical preference for websites that work across platforms and from a resource commitment standpoint.
In an ideal world, downloads in YTM would have arrived soon after youtube.com added the capability for videos at the end of 2021. Regardless, it’s here 2.5 years later and works as expected.
Source 9to5google.com