Were older ironclad modernizations worthwhile?

Were costly modernizations of 1865-80 ironclads a worthwhile alternative to scrapping them?

Often not. Many third- or fourth-generation ironclads would still have been discarded.

The case for retaining adaptable late-Victorian cruisers does not extend to every earlier ironclad. Many ships from roughly 1865-80 would still have been discarded despite costly modernizations. By Fisher's period they represented a third or fourth technological generation, so the case for further investment was weaker. Reserve value still had to be assessed ship by ship.