I’m pretty sure that YouTube has been compressing videos harder in general. This loosely correlates with their release of the “1080p Enhanced Bitrate” option. But even 4k videos seem to have gotten worse to my eyes.

Watching a higher resolution is definitely a valid strategy. Optimal video compression is very complicated and while compressing at the native resolution is more efficient you can only go so far with less bits. Since the higher resolution versions have higher bitrates they just fundamentally have more data available and will give an overall better picture. If you are worried about possible fuzziness you can try using 4k rather than 1440p as it is a clean doubling of 1080p so you won’t lose any crisp edges.