This is not how I would define modern software. High customization was more of a trend in the late 90s to the early 00s.
People were crazy about themes, skins, custom fonts, colors, mouse cursors. Winamp was famous for that (except that "nobody wanted to see a Winamp 4 skin"). Myspace was the big social network before Facebook, and was well know for the sometimes excessive level of visual design freedom it offered to its users. It was also a time where you had dockable toolbars everywhere, customizable menus, etc...
Modern apps usually don't let you change much. I think we have a bit more customization than a decade ago, but it is not as wild as it used to be, in fact, it is rarely more than a "dark mode" toggle.
People were crazy about themes, skins, custom fonts, colors, mouse cursors. Winamp was famous for that (except that "nobody wanted to see a Winamp 4 skin"). Myspace was the big social network before Facebook, and was well know for the sometimes excessive level of visual design freedom it offered to its users. It was also a time where you had dockable toolbars everywhere, customizable menus, etc...
Modern apps usually don't let you change much. I think we have a bit more customization than a decade ago, but it is not as wild as it used to be, in fact, it is rarely more than a "dark mode" toggle.