What about if it were an explicit practice in 5e core books and adventures, for all the proper names to be customized by each DM?
There'd be a little chart in the appendix giving alternate names or syllables for each proper name--place name, major NPC name, and deity name.
These could be flagged by enclosing the proper names in a box.
For example, for a 5e Temple of Elemental Evil the name "Hommlet" would always have a box around it. There'd be note in the beginning of the adventure, saying that the DM is supposed to pick their own name for the town and other proper names.
A small chart in the back of the book would give suggested alternate names for Hommlet. There'd even be the option of randomly rolling the name by using the table of village name syllables which are phonaesthetically similar to "Hommlet": "Gommville", "Kommstead", "Ommbury", etc.
That way, the 5e generation of players will still share a common experience of having played through the iconic adventures, while at the same time, more vigorously supporting a culture of kit-bashing and homebrewing.