Have they? I hear people say this on Hacker news but i've never heard it anywhere else, people seem to be using the internet just fine with Google as there main search engine, what is the alternative? Bing? It's still trash and Bing Chat is like a worse version of ChatGPT, I don't see it replacing Google currently.
I would bet that a good chunk of users don't know that you can change the default browser or search engine, or at least don't think to do so. They might not like the UX, but they have other things occupying their focus and muddle through a bad experience with their phone or PC, just like they do with many other mediocre interfaces throughout the week.
If I want to find artists, lyrics, locations, results of sporting events, other special events... I'm not sure all the things, but DDG doesn't even compare.