Although I would dispute that we have much in the way of real IC services now as the onboard facilities aren't good enough.
To be fair there are no facilities on ICs in several countries such as Belgium and the Netherlands.
Manchester to Barrow is, in 1990s-DB terms, a RE - subsidised and mostly used for overlapping short trips. CrossCountry is a bit more like what InterRegio was. DB has long had some very long-run REs - I recall riding one in east Germany somewhere that had an end to end time of just over three hours.
In effect DB has had some car-like "model inflation":
ICE - has largely replaced what was IC now it's expanded so much including slower routes
IC - has become near enough what IR was minus a few uneconomic routes
IR and D (other than specials) - gone
(RE, RB, S still there as before)
With DB there's also the slight complication than ICE/IC are commercially operated without subsidy and RE/RB are tendered by the Bundeslaender. Thus there were (and probably still are) odd cases like Berchtesgaden where an IC would become a RE at a certain point due to subsidy kicking in. You could compare it in UK terms to the idea that a GWR Paddington to Penzance might in theory run commercially to Plymouth as ICE then become a RE providing a subsidised local service thereafter.
RE doesn't necessarily mean "doesn't stop at all stations", by the way, there do exist all-stations REs. The general difference was classically that RE was used for services in a local Takt and RB for randomly timed branch lines and sporadic local services on some mainlines (which do exist in Germany), though it's not totally consistent. There also used to be a StadtExpress (SE) category that was very similar to a lot of South East commuter services like Chiltern or LNR - all stations to the edge of the S-Bahn system then fast into the city, but that isn't used any more and such services mostly became either RE or S.
