Like others, I have been through five editions of the same game, plus a number of spinoffs and variants. For almost four decades, I have read, played, discussed, argued, and shared advice from a large number of sources and materials, including blogs, forums, videos, magazines, and table groups.
So when I looked through the 5e DMG for the first time, I was underwhelmed, to say the least. Needless to say, I have not felt any compulsion to open it since except on the rare occasion I needed to reference a particular rule or item. But as far as being innovative or inspiring, I find myself looking more often at pevious editions (particularly 4th Edition stuff), articles and videos from alternate sources, or other game system guides for GMs.
This thread, however, got me curious enough to see if I was missing something. I hadn't cracked the book open in a long time, so I looked over it again when I had some time to kill. As it turns out, nothing had changed and I still felt the same way.
However, I now recognize that the book is a collection of some of the best advice learned through all the years of design, development, and practice with the game through every iteration since the beginning. For someone like myself, it doesn't really offer a lot of new or innovative ideas. But for newcomers, new DMs, and even lapsed players, it provides a solid, stable foundation of advice and tips learned from the past, adapted for the present, and should be carried forward into the future.