I suppose it depends on how you define “architecture”. I usually take it to mean something along the lines of the properties of a software design that are difficult to change once determined and/or that potentially affect the entire code base and/or that are expected to last for a long time. Given some such definition, it is certainly very expensive to change architecture, and therefore relatively unlikely that you’d want to rewrite on such a sweeping scale. That still applies even if the architecture you’ve developed after a while isn’t what you’d ideally chose if you were starting over.

I don’t really see any qualitative difference from any other large (but not that large) scale rewrite, though. To me it’s still just a quantitative cost/benefit question, albeit one where the cost is very high so you probably need to have some severe obstacle to overcome before the big rewrite is justified.