Minimalism is also a tradition in logos. A logo needs to serve many purposes, one of which is being recognizable even under poor visibility. Many national flags are the height of minimal design, because one key goal for them was to be seen in battle so you knew where your side was.

Modern technology has different reasons for a similar purpose. Resolution may be poor because of your screen or network rather than battle smoke, but the idea is similar.

The OUP logo isn't a battle flag, and could afford more detail than this logo. But OUP is a living entity. Its history is important, but so are its ongoing contributions. They don't want people looking at their books and thinking, "This logo is very old-fashioned; maybe the book is also out of date."

Were it me, I'd have at least hinted at its prior logo. To me, the problem with the new one isn't its minimalism, but its lack of personality. You don't need a lot to have personality; the Twitter logo is very much theirs. Even the Facebook "f" logo, dull as it is, at least has a letter linking to them. (A circle isn't an O; it might even have worked better if it were an O with the same theme.)