I do not think that anyone looking at a Leica today is wondering if they should switch it for a wet plate alternative. They will be comparing them with other 35mm cameras (or possibly 120).
The main photographic characteristic of the Leica is the viewfinder/focusing system. You can get that vastly cheaper with older fixed lens RF cameras, as well as Zeiss/Voigtlander bodies. And you can approximate it to some extent with Fuji xpros or similar.
When people talk about the “Leica experience” today, I strongly suspect that they mostly mean “shooting with an expensive chunk of extremely expensive finely made brass”, since that is really the only meaningful difference between a Leica and other rangefinder (or rangefinder like) cameras. And that has very little to do with the photographs that you can take...
The RF experience is the same with other cameras, in as much they are cameras as well. Having used Canon and Nikon RF cameras, I can tell you the viewfinders and RF patches do not come close to that on Leicas. Not remotely close. My Bessa R3a was close, but the rest of the experience was lacking from the clanky shutter to the coarsely made (in comparison) pieces. But I think I may be one of the few people that actually liked the manual frame line selection, as it allowed me to have just one LTM-M mount and I could use that on all my LTM lenses. But I digress...
Apparently the Zeiss Ikon ZM (which I have never used) is a worthy competitor but it's price now is more than an M6 and, from what I've seen, the same as an M7 (used). So the closest competitor costs the same money, but is made out of stamped metal pieces.
There is no fixed lens RF camera that is anything similar to a Leica M either. You know that too, but again, I guess because it is also a camera so it must be the same thing.
Interestingly, I have a Fuji GW690III which while has a fantastic lens, it's rf patch is such a tiny dot the Leica puts it to shame. One camera that I have that, IMO, matches up really well is the Hasselblad XPAN/Fuji TX. It has an excellent VF, an excellent RF patch, and a really nice feel to use. And it is huge money. More than used Leica money. I think there is a pattern here.