Was this "portability" issue such a problem in earlier editions?
I cannot comment for 2e, since I have never tried it before. As for 3e, I felt I was able to adapt certain aspects of FR (I don't use Eberron, so again, no comments for that) seamlessly into my normal campaigns, such as thayan enclaves (basically low-level magic k-marts). Regional feats, while conceptually unique, weren't really that much more powerful compared to normal PHB feats (save for maybe 1 or 2 exceptions). Same for other features such as bonus starting gear. PRCs proved a little challenging, because quite a few were intrinisically tied to mechanics and flavour unique to FR, but nothing some rewording couldn't solve.
As for cities, I never felt that they carried much "setting baggage". In the very least, I don't see how cities such as Thay or Waterdeep, or organizations like the cult of the dragon would be unique only to FR.
I cannot comment for 2e, since I have never tried it before. As for 3e, I felt I was able to adapt certain aspects of FR (I don't use Eberron, so again, no comments for that) seamlessly into my normal campaigns, such as thayan enclaves (basically low-level magic k-marts). Regional feats, while conceptually unique, weren't really that much more powerful compared to normal PHB feats (save for maybe 1 or 2 exceptions). Same for other features such as bonus starting gear. PRCs proved a little challenging, because quite a few were intrinisically tied to mechanics and flavour unique to FR, but nothing some rewording couldn't solve.
As for cities, I never felt that they carried much "setting baggage". In the very least, I don't see how cities such as Thay or Waterdeep, or organizations like the cult of the dragon would be unique only to FR.