I would love if we use this opportunity to move away to webpack assets vs rails asset pipeline.

We're trying to, but what does Rails 5 have to do with it?

Reply from Ohad Levy:

Many of the asset ge,s are not compliant with rails 5 (e.g. wrong dependencies in spec file etc).
if we move away from using those, we wouldn't care much which version of rails we are using (and really, there is little connection between client side assets and rails version).

(Edited by Dominic, the comment was incorrectly edited instead of being replied to.)

As a general hint: Rails 5 needs Ruby >= 2.2.1