This page collects various failures of Google's "world class developers". Everyone is welcome to contribute.
Android file manager
Both "Files by Google" and Android's built-in file manager (DocumentsUI) lack basic features one would expect from a file manager. For example, there is no scrollbar. You can not see the total size of selected directories. You can not limit searching to one specific folder but you have to search the entire storage. There are no filters like date range. The search feature only returns up to 24 results, an arbitrary limit.
Most importantly, after tapping on "copy" or "move, it doesn't stay in the current directory, but opens the Download folder instead. This means, if your goal is to move files to a subdirectory of the currently viewed directory, you have to manually navigate all the way back to the directory you were in. This is something even Windows 95 did better.
GBoard (Google Keyboard)
There is no option to turn off the one-hour clipboard time limit.
Google Calendar
Lacks a "jump to date" feature. This is something Samsung had in the early 2010s (but curiously removed with the S6), and Nokia had even in the 1990s, for example on the Nokia 7111.
If you want to check what day of the week a specific date was, you have to manually scroll to it.
Google Chrome
Mandatory pull-to-refresh, data lock-in, lack of customization, and more. See Everything wrong with Chrome.