In the world of photography, either color or black and white, we often use products that are not "state of the art" because we like what they do for us in the creation of our images. I would think that the Solaris films, whether they are behind-the-times or not, might offer a "look" that is different and I, for one, might consider this as another paint on my pallet for creativity.
There are lots of us that use "old fashioned" single coated b/w films from Eastern Europe for the "look" it gives us. There are some of us who do wet collodion work, for the "look". Certainly not state-of-the-art.
It is true that in general color films from Kodak and Fuji have become "better" in many ways, finer grain, better keeping qualities of the processed image, more color saturation options, higher ISO's, etc., but those are only some of the attributes that make a film worthy for creating our individual visions.
Oh, and the Solaris films, according to their website, are available (in addition to 35mm) in 126, 110 and APS, which can keep some cameras going.
Phototone