To be fair....you are pretty much spot on.
The unit we had was clearly marked "For VFR Use Only".
I trained on Decca in 1968 when in Army Flight School.
When I arrived in Vietnam where Decca had once been used....the only use we got out of the fit was the left over Plexiglass cover for the Decometers which made a handy note pad for writing down Artillery Fires Data using a Grease Pencil (wax pencil I think you call them).
All of the Decca equipment had been removed as it was pretty much useless in the configuration we had....the sticky tape on the scroll maps in the tropical heat held together about as well as a Pilot's Union at Contract time.
I recall flying around in Norwegian Waters where Flight Levels within the Ekofisk Field was predicated upon Height based upon their RadAlts which was a bit awkward as our aircraft had three BarAlts but no RadAlts.
Remember the Rwy 27 Decca Approach at Sumburgh?
Think about doing that at Night in bad weather....Single Pilot with no Autopilot....Map Change, Key Change, and Re-set the System...in some Snow and lots of static electricity to ensure you had to do at least a couple of re-sets.
Yes....we have progressed and I hope the current crop of Pilots continue to seek improvements that make their lives safer and easier.