renders the whole thing useless.
I disagree. If we'd allow only those properties that don't affect layout to be redefined for the
:stuck pseudoclass, we'll get infinitely more control over what we have now (nothing).
And those properties that don't affect layout are those that are used for sticky elements in real world use cases. I guess the most popular property to redefine on the stuck state would be a box-shadow.
The layout-changing properties could be useful too, but why can't we go iteratively and allow just a subset of properties from the start, and think out the solutions to enhance it later?
Developers need position sticky already and need this pseudoclass for them too, saying “there are issues, so you won't get it in any form” is not productive.