This made me wonder: how long will we really keep every feature of CSS? … How long can we reasonably go without removing the old? How viable is this approach over time? 100 years from now, will people still be able to write
floatin their CSS?
I can definitely see a future where either a new browser engine or a significant engine rewrite decides to support only a more “modern” subset of the CSS spec — especially if it’s Chromium. I don’t know the first thing about writing an engine but I think for that to work it’d have to reduce the net maintenance burden even after considering how to handle rendering sites using older CSS.
I could also see directional properties being deprecated from the spec in favour of logical properties (e.g. margin-inline-start replacing margin-left) but this seems so far away. I’d be pleasantly surprised if that began by the end of this decade.
(I actually think float is an interesting but ultimately bad example since using it for layout was always a hack. It was and continues to be useful for its intended purpose, even if seldom used.)