Furious did not define the full potential of Britain's 18-inch gun

Would British 18-inch guns have remained too troublesome for later capital ships?

Not necessarily; the Furious installation was compromised by its platform, and a sustained program would likely have developed a different, improved weapon.

Single-gun mountings were already unattractive for ranging and salvo control, which signals how heavily Furious constrained the installation. The gun fitted to that hull should therefore not be treated as the mature endpoint of British 18-inch development. A genuine capital-ship program would likely have continued refining the weapon much as Britain persisted with Nelson's 16-inch guns. A later follow-up notes that moving from a 40-calibre to a 45-calibre design would address much of the short-barrel problem, while leaving the final mounting and ship design to be solved together.