Dunno if this is design or construction, but anything less than a full stainless steel case is usually enough for me to toss a watch from consideration.
I still have 4/5 gold/capped/plated watches - acquired early on in my addiction - but I now, like you, only consider full stainless steel.
I’m not a big fan of date windows unless they are discrete or don’t bugger up the symmetry of the dials … and don’t get me started on Cyclopes … the more apt nomenclature here would be browneye
Completely agree on the cyclops. I'm not a Rolex fan generally, but that particular feature ruins the dial for me.
I could compile a (vintage only) list, so let's get started... 1) mixing Roman and Arabic numerals on a dial 2) recessed crowns that are difficult to manipulate (most) 3) embossed indices (though a few, e.g. IWC, were very well executed) 4) lugs that feature no demarcation between them and the top of the case 5) high-polished case backs (they scratch much too easily), e.g. Longines Silver Arrow
Out of balance crowns, which can be too large but are generally too small. Not only do they look frail and appear to be an afterthought, they can feel tinny and be difficult to use for winding or adjusting the watch.
Front loader, the watches without case backs that require removal of crystal, split stem to access the movements
Many more details through this link: https://www.rolexmagazine.com/2012/09/the-history-of-california-dial.html
Date features, especially if in combination with day features. A few live here, but they are not my favorites. A date feature causes an otherwise appealing dial to appear as if it has an ulcerated sore. Besides which, I never consult the day date features, but feel compelled to set the silly things if I don a watch having them. They're just fiddly and pointless for my purposes. Round watches look honest, open, and happy. All other watch shapes look a bit devious or sinister somehow. Only two on hand that aren't round.