I'm interested in would you leave this or would you "try" to correct or upgrade and if so to what extent and why.
Those are four excellent photos.
I commonly work with housing stock that spans from being first "electrified" some years to decades after the house was built, to being wired during original construction. This housing stock has been inspected by electrical AHJs that were first called into existence, by State statute, at the very beginning of the 1900s.
I've seen similar installations, to those in these photos, that were done as part of the original electrification, and, also, as part of subsequent branch circuit extensions.
I agree that the K&T - BX transition is missing supports, which implies that it was never inspected at the time of assembly. In my experience, the BX extension may date back easily into the 1930s, and was not required to be grounded in this application, unless the Utilization Equipment supplied required grounding.
In my opinion, the first (left hand) photo also shows splices (flying splices) that are missing supports.
In the areas that I work in, some areas have local ordinance that requires removal of exposed (attic & basement) K&T that is in excess of a maximum of 18" in length. The 18" length allowed to remain provides, generally, for easy installation of a junction box and the transition to another wiring method, such as NM. - - - This ordinance is invoked upon Code Compliance and service upgrades. A Home Inspector's observations don't invoke the ordinance.
As for my opinion, the attic is exposed to additional temperature extremes and humidity swings that provide greater environmental stress on the common K&T conductor insulation. Careful examination will determine brittleness, if aged enough. Any use of the attic by the occupants adds an additional stressor, depending upon the use(s) and proximity to the K&T.
After explaining the local ordinance guidelines, I'll offer my assessment of current state of the insulation and its exposure to additional stress. If the assembly is much like that shown in the right hand two photos in the OP, I would classify it essentially pristine, and if the insulation is still supple and the area is isolated from use by the occupants, then there is still no particular risk, IMO.
My last observation, with respect to insulation, is, that if future insulation is added against any exposed K&T in this attic, that the K&T should be protected (not practical, IMO) or replaced with modern methods. If the existing insulation was placed prior to the late '80s NEC change that created the requirement to protect K&T from embedding in thermal insulation, then the install, as pictured met the NEC of the period. Many times, placing J-boxes at the drops into the walls below is all that is needed.
