KX or KM, even MX, are far less hyped...
Actually MX had and still does have, quite a hype too, but mostly a deserved one. K1000 ??? I'd take any other Pentax MF body before K1000, and not only due to pricing. A so much older Spotmatic can feel so much more refined, and not only against K1000 but many well known models from all major brands.
I don't agree mechanical cameras are not worth looking into. Lots of them are still going strong 40-60 years past their prime. Whether learning manual shooting is easier with more modern model that has all the extras on top of a manual override is a matter of choice, and up to a debate.
Does that auto stuff help learning manual, or is it getting in the way? Problem I have is, auto is there, and using it as a way to learn manual is not all that straightforward. It sure can be thought of as such, but it is more like studying for a test with prep-books, vs. learning the principles and applying them correctly in solving presented problems.
As for Zenit - well, shutter speed limitation alone makes it one of the least choices. Viewfinder? dark and limited, even the 12XP made no dent in how it behaves. It is a rather crude machine and can damage any surface it drops on. The one plus is the standard lens Helios, but it's a gamble anyways. Odd-ball production practices and apparently no quality control can have you end up with either a lens with so-called clinical, downright astounding optical quality or a dud not worth its weight. So a Zenit is more of a historically hysterical proof of how not to produce an otherwise presumed precision instrument. Still, with luck, it can take wonderful photos.