FWIW, I own a pair of Montis ESLs, which were rendered "older models" when the current line of ML ESLs (including your 13s) was introduced. ML also moved their operating headquarters from the US to Canada. And the dealer who sold them to me dropped the product line.
I suppose, early on, I felt a bit worried that my investment had taken a hit, and I had a modest fear of abandonment. But the fact is, that isn't what happened. My Montis, now ten years old, continue to perform well, they do the job they were intended to do, and when I've run into issues, ML Support has solved the problems effectively and inexpensively. Beyond this, I believe ML continues to attract a healthy following of interested audiophiles. In one group of Hi Fi enthusiasts to which I belong, there are several happy and enthusiastic ML ESL owners, and their pride of ownership is immediately evident based on what they have to say about their listening experiences.
The fact is, an ESL, even a ML ESL, isn't for everyone. Some don't like the size or the looks or the way they sit out in the room. The interaction of this bipolar radiator with the room is particularly complex and not everyone has the patience to deal with this. The ESL is a generally capacitive load from midrange to treble and needs better than the average mill of amplifier and source to bring out the best in it. Despite this, however, there still are a healthy number of individuals who are pleased with the results. The internet also makes the individual owner's experience ever more broadly shared with others, which naturally serves as a form of advertisement.
I'd also like to point out that ML ESLs actually do employ crossovers, so saying "there's no crossover" isn't strictly correct. The bass unit is a separate source from the panel, and the crossover between the two is not only necessary but extremely complex. Sure, there's no crossover from mid range to treble, and that's indeed an asset, but the benefit of this smooth transition can easily be blown by not properly dealing with the impact of the back sound radiation relative to the front and the beaminess of a (nearly) planar radiator. It is also important to realize the panel is driven through a transformer which, of necessity, contributes it's own coloration characteristics.
Beyond this, there are in fact non ESL speakers with multiple drivers whose crossover characteristics effectively disappear, so crossovers, while potentially troublesome, aren't always. I own two sets of them: The Dynaudio Contour S1.4 LE and the Dynaudio Heritage Special. The crossovers, both low pass and high pass, have slopes of 6 dB per octave which inherently have this perfect phase blending property. Now, admittedly, it's hard to find any old loudspeaker with tweeters that will tolerate a high pass cutoff of 6 dB / octave - Normally, this means early death to the tweeter when strong upper midrange signals are encountered that melt its voicecoil. The Dynaudio tweeters in the aforementioned are designed capable of withstanding high out-of-band power which makes this mode of crossover operation possible. What do they sound like? Like they have no crossovers, which is (in part) why I bought them and enjoy them so much.
Just my two cents.
