I have to keep learning this lesson over. A camera lens is a tool. They do a job. There are tools that are intended to do many things, like a Swiss army knife. There are camera lenses like the Swiss army knife. Canon makes a 28-300mm zoom. However, it needs its own little cart to carry it around. It seems to me a tool that defeats its own purpose.
I owned a 70-300mm DO, a while back and sold it. It was not quite as sharp as my L lenses. But I am getting ready to buy another copy. I am hoping to do a lot of travelling in the next few years, and I want a long zoom I can carry in my pocket. I rate the lens a 10 because, as far as I know, this is the only tool on the market that does the job I want done.