What's sad is that Inbox stopped evolving almost immediately after they released it. This seems to be a thing at Google. Release something, hype it, and then just walk away instead of maintaining and improving it. If there was anyone working on that at all in the last 3 years; sorry I failed to notice that there was anything happening at all. It looks to me that there was a skeleton maintenance team at best. So, it looks like there was some infighting and the Inbox team got starved of resources. Gmail on the other hand was improved a lot over the past few years.
In general it strikes me that essentially all attempts by Google to do a bait and switch of their products in the past few years have been impopular and somewhat underwhelming in their outcome. They've killed a lot of popular products in favor of things that then flopped. They've repeatedly walked away from products that maybe had issues but were entirely fixable only to replace them with something worse.
There's something deeply wrong with how Google is being managed since Alphabet was created. They are lacking a clear direction/strategy. Is it Fuchsia, Chrome OS or Android that is going to be the OS of choice? I'm not sure they know the answer themselves. I'm not sure their OEMs know either. My advice, kill two out of three and get it done within the next 12 months. IMHO, Android would at this point be by far the most disruptive thing to kill. There's a big risk of forks surviving any attempt by Google to kill that and ending up being a headache for Google.
Similarly, which of their billion chat clients are we supposed to actually use at this point? Same advice, pick one, kill the rest ASAP. IMHO keeping and fixing hangouts is the best course of action at this point. It's the only one that's been around long enough to actually have a user base (despite it's many flaws and terrible UX).