There's too much chrome. There's no way that I've ever been able to find to remove the fat fixed message header in reading view to see more of the message.

There is too little in modern "nice" designs... on VS Code for example all the title bar is filled with junk buttons by default, and you have to search hard for a single pixel to be able to grab that window and move it. Decades of usability research thrown out the window thanks to Mac and web folks dictating the trends.