Forcing an API user to pass in a content_view_id when filter id along would suffice seems like added complexity to me. I really don't see the harm in having a non-nested route.

Moreover, the problem I see with nesting some routes and not others is defining a clear rule to the user. Like why is filter nested but other associations like environments not? Environments don't make sense outside of an org either but yet it's not nested.

With having an unscoped route for every action, it seems much easier from an API user standpoint to not have to guess if a route is nested or not. You always know there is an non-nested call you can make. The problem with v1 is you never knew if it was nested or not. Is the route `/systems/:id/subscriptions/:id` or `/subscriptions/:id`?