Not necessarily more complex, but not less complex either IMO. I often say complexity can’t be eliminated, only spread around differently; I think we’re seeing that here.

2 ways to do something is more complex than 1.

But it's more than just the syntax of the code. It now means new lint rules, new coding standards in projects (some will allow => assignment, some will encourage conformity to legacy code, and others will disallow it entirely). There will be new Rubocop rules and other editor configs to update for proper syntax highlighting.

Syntactic changes like this with little obvious benefit need to be looked at skeptically. Just because something can be done, doesn't mean it should be.

Or this one

cat => person.pet