Well, as someone who spends most of his fun money on both Swiss watches and Porsches, I agree that classic Porsches are also in a bubble, but I'm not simply talking about vintage watches (btw, have you seen the price of vintage Milsubs and Daytonas lately?) The retail price of a new Submariner Date has gone up almost 90% in ten years, which is around double the increase of a Porsche 911 over that time, and a Rolex is still a mass produced watch, machine made watch. I'm not talking about Patek Philippe here.
Watches do straddle the line between being a tool and a piece of jewelry/art. A Squale is more of a tool, a Patek is more of a piece of art/jewelry, and Rolex is somewhere in between, although they all do still provide the function of telling time. The difference between watches and the other things you mentioned, like paintings and cars, is that I only have one space on my wrist to wear a watch (unless I become part of the double wrist'ing club

,) and my Apple Watch has become far too useful to ever leave at home. So, do I keep a drawer full of Swiss watches that I never wear, simply to ogle at their beauty and appreciate their movements from time to time, or do I sell them and put that money towards other interests, like another Porsche? Granted, I do still have a hundred year old gold pocket watch that I don't actually use, but it is an family heirloom that I can't sell, so it sits in a safety deposit box.
I'm not saying that the sale of Swiss watches will go to zero, but we've already seen the Swiss industry take a hit in the first year of Apple Watch sales, and I can see that taking a longterm toll on the value of both new and secondhand Swiss watches, particularly the low to mid-level, mass produced brands like Hamilton all the way up to Omega, Rolex, IWC, etc. Patek, AP, and other smaller high end makers will likely also feel the pinch, but that's where the true enthusiasts will probably double down and focus their energy, so I can imagine their prices holding.
The bottom line is, many of us dream about nice watches for so long that we allow ourselves to be duped by the pricing, which is pure Veblen strategy, so, when something threatens that illogical thinking, feelings start getting hurt. I've spent an embarrassing amount of money on mechanical watches in my life, and I've loved them since I was a child, but I'm just being honest with myself. My Submariner Date probably cost less than $600 to make.
p.s. I don't understand your use of the word garish.