It is indeed a long way off. I am still frequently seeing production environments today using 5.16 and occasionally some as far back as 5.8 so there won't be universal coverage of any to-be-introduced language features for well over a decade after release. The consequences of the decision may not be seen for a long time but once the decision is made it will be very difficult to avert them entirely.

I'm sure that none of us have the expectation of perpetually maintained modules forever, gratis. My concern is that the incentive to maintain an already-widely-used module will likely be reduced if the language is extended to include some/most of the functionality.

The first version of Corinna lacks a lot of features which have been added to e.g. Moose or Moo.

Intentionally so - the docs make a big noise about it being an MVP. Perhaps that is all it will ever be: such that to do anything beyond that minimum would require one of the already extant alternatives. That might just be the best of all outcomes.