I enjoyed clicking through the slides that Peter Ramsey put together. All good points, I think. It’s mostly about the onboarding process, which has some pretty hilariously bad issues, like these FIVE DEEP popups:

There is a good bit about how Google warms you up with agreeing to an easy-to-agree to feature before hitting you with the “give Google data” question where you’re likely to agree to it because you’ve been primed to.
I might argue that the actual day-to-day usage of the product is actually pretty good and doesn’t suffer this same level of messiness. So much so, that every time I try to switch away, Gmail somehow has such gravity it pulls me back. And its not usually about features, it’s usually about accomplishing some task. I was on Shortwave for quite a while. It’s good! But Gmail eventually got me back because of the odd task here and there I just couldn’t get done in Shortwave.