This is very much not the case both ways. Yes, you could use DuckDuckGo instead of Google. But by the same logic you can always use some local DSL provider for your ISP. That is still a thing in most places. Of course, you will get 1.5Mbps instead of 50Mbps via Comcast, but it is not like DDG provides the same range of service as Google either.
1. [Opinion] As someone who uses DDG for 95%+ of my queries, the sacrifice is orders of magnitude less than using the local DSL provider in your example.
2. [Fact] Switching ISPs has a much higher cost. Switching back to Google for a few minutes if DDG isn't getting the job done is three keystrokes: " !g".
The question isn't whether a viable competitor exists, it's whether a viable competitor that respects privacy exists.
I'm in a Detroit suburb, but I guess I'm an outlier.
The argument is also a bit of a red herring, because even with vibrant DSL competition, the same argument could be made by the monopoly ILEC against a privacy-respecting CLEC.