CEP for KH-55 is listed as 25m.
Not sure where you are getting your figures from but that is way too accurate for a missile with no terminal guidance system, just a terrain comparison system for flight along the way.
With its nuclear payload it would not need that level of precision.
There was also a optical terminal guidance version the SM, that was for precision strike.
The Kh-55 is nuclear armed and has little need for that level of precision. The Kh-55SM is the same missile with saddle tanks to extend the flight range from 2,500km to 3,000km and also uses a nuclear warhead.
The Kh-555 has the terminal seeker of the Kh-101 and the conventional warhead and has a CEP of 3m to 5m and a conventional HE warhead.
Missile threat lists the KH-555 range as 3500 km.
I believe its range has been revealed to be between 2,500km and 2,800km...
They started making Kh-55s in the late 1970s, but replaced it in about the mid 80s with the Kh-55SM with saddle fuel tanks and slightly increased range.
The first Kh-555s were converted Kh-55s... it was Kh-555s that were used in Syria along with Kh-101 which are both conventionally armed cruise missiles...
Yeah I think the KH series is pretty awesome and can just do with targeting upgrades. Other then that, easy to build, probably lots in stock for cheap upgrade, 3500km... what more do you really need.
There were essentially three families... the Kh-55, which improved to Kh-55SM and then the conventional Kh-555, and the 3M10 Granat, which was the naval system that has since evolved into the Klub and Kalibr system (Klub for export Kalibr for domestic use).
The Kh-101/102 is an enlarged and extended range missile family... no longer 533mm calibre for launching from torpedo tubes and no longer 6m long for fitting internal bomber weapon bays the new 750mm calibre 7.4m long missiles have much better flight range and will likely replace sea based versions too.
As you point out the older shorter smaller missiles are just as useful as they ever were and you could fit huge bundles on trucks and trains and shipping crates...