Earlier quoted context omitted.
But what if the latest version simply isn't something you want? Exactly. Even worse, what if the old version was what you wanted, and now it's gone? For example, Google's book reader on Android. I started using it frequently about 6 months ago. Since then, every UI change they have made has made the experience worse for me. The only reason I still use it is that it does have one big advantage over the other readers I…
I know how you feel. Gmail's interface has become incredibly complicated and every change feels like a step backward. But as much as I don't care for Gmail's current interface, I can't and don't expect Google to support older web interfaces. If I really wanted interface consistency, I would run my own mail client.
That's what I do; in fact, I run one that's unlikely to change its UI much (KMail from KDE version 3, the Trinity Desktop Environment build).