I kind of agree. Look at this: Mavericks OS X 10.9.5, resizing windows in different apps.
It should be noted that it's up to
how the app was written and on what foundation its code-base rests. For example, Firefox 70 is better in all tasks than every version of Safari in both Mavericks and High Sierra, and its UI looks clever and nicer than that of post-Mavericks Safari, especially on
non-Retina screens (that can be applied to other apps and the OS as a whole) – all colors either washed out or over-saturated, and the overall tonal rage instills depressing mood contributing to tiredness and inability to fully concentrate on my work as opposed to when I switch to Mavericks which feels like a native habitat and immediately sparks my energy.
High Sierra is the least liked macOS on my approval scale, though. Runs hotter, window transformations range from very quick ones to stuttering (full-screen – normal, going white before switching back to non-fullscreen). The only positive thing is I have newer versions of apps or just apps that were never made for older versions, otherwise HS is not of a very high value for me.