The main issue I had with this episode is it's confusing as heck, took me quite a while to realise what was going on, but once I got it I got it.
This is a 'what if' episode of 'if Grace and Frankie hadn't cohabited and learnt from one another' (happening as a self reflective flashback to what could have been), consequently Frankie, having never learnt from Grace how to be more independent and pragmatic, has basically become a tiresome hippy hanger-on, where-as Grace, without Frankie's influence, has become a cold and hard hearted plastic faced rich biatch, grasping for anything she can carry to fill the emptiness in her heart.
We also see how everyone else isn't doing so well, there's a lot of bad vibes going round, and we explore all kinds of consequences.
When we've known them as such well rounded, caring and giving people in the rest of the show, seeing Grace and Frankie as their worst selves is really hard, particularly Grace who is just beyond repulsive, so I can understand why it's not well liked by other reviewers, but it makes its point quite vividly.
They need one another and the world needs them.