In my opinion, which may not be popular, Leitz began the transition to a maker of luxury goods rather than professional tools when they brought out their first SLR. and has been headed down that road ever since. The original 1966 Leicaflex lacked TTL metering, which had been available in several Japanese models for a few years. In addition to the normal lens, the only additional lenses were the 35mm, 50mm, 90mm and 135mm focal lengths. While the quality remained superb, very few professionals took to the system, and the price kept all but the most affluent amateurs from considering it. In 1968 they finally got TTL metering, but the lens range did not expand much. By 1970 a Leicaflex was going for $738 ($2,600 in 2020 dollars) while you could get a Nikon FTN for just $381 ($1,345 in 2020). 1970 Leicaflex lenses included a single model each in focal lengths of 21, 35, 50, 90, 135, and 180mm. The 50 was the only f2, and most of these cost half as much or more than the Leicaflex itself. By comparison, Nikon offered lenses from the 6.5mm fisheye to the 1000mm supertelephoto. Leica's 35mm f2.8 went for a pricey $213 as a basic street lens, while Nikon offered an equally good f2.8 model for $179.50 and a fast f2 for just six bucks more than the Leica f2.8 model. Nikon's wonderful 200 mm was only $219 and Leica's 180 mm was nearly twice the price. I could go on, but you can see where this is going.
Nikon and Pentax both offered well-finished durable cameras, full lens ranges, and a reputation for ruggedness that was well earned, at about half the price. No professional on a budget or needing a rugged camera would have even considered a Leicaflex, although many stuck with their Leica RF models for many years. Eventually the superiority of the SLR system for many professional uses (particularly close in and long lens work) made the decision a non-decision. Pros working in the field went to Nikon (and eventually Canon, as their glass became great) and studio pros stuck to medium format.
Leica became the Montblanc of cameras then, and has been so ever since. They still make wonderful gear, but it's not rugged or versatile enough for most professional use and too expensive for all but the most status conscious and affluent amateurs.
That said, I'd love to have a "modern" Leica (and the used Leicaflexes are now relatively cheap on the used market). I've stuck to the Barnack Leicas, and I love them - the best fit and finish of any of my many cameras. I'd love to own an M-4 or even M-6, but I'd have to trade virtually all of my other kit to afford one. I can't afford that kind of scratch for what basically is a necklace with an amulet on it.
Love the brand, love the quality, but it's just not worth it to many of us who didn't buy into the systems many years ago. This makes me a little sad.
Andy