This is not true. "Switch your DNS" hasn't worked for while. It didn't work for the TikTok ban. The ISPs are not incompetent.

If the DNS change solution ever works, because they are half-assing it for whatever reason. And this time they apparently aren't.

And in any case, this is a really bad way to look at this situation. Your response to the government taking the next step in what looks like a very well planned power grab and move towards authoritarianism shouldn't be "well the ISPs suck here".