One example is the calendar that keeps getting worse release after release, so much that I had to switch to macOS calendar.
Global Inbox also got broken several years ago and never fixed, since it seems all their energy goes into making things prettier at the expense of making things work.
And even that is a matter of taste. They tend to make things resemble some combination of an Android app aesthetic and a Google Chrome aesthetic. For example, replacing dialogs with item hierarchy trees with a scrollable flat web-form-like preferences page.
At least they backed out of the switch to monochrome folder icons. 8-\
Global Inbox also got broken several years ago and never fixed, since it seems all their energy goes into making things prettier at the expense of making things work.