The second has a different meaning, and the third is incorrectly phrased. You can say: People no longer take part in the hustle culture. People of my age no longer participate in hustle culture. Lots of people are no longer convinced that hustling all the time is a good thing. He and his wife are on the same wavelength concerning the issue of work/family balance.

Regarding the first one, it can be used that way, but the preposition "the" isn't necessary in front of "hustle culture." So, you can just say "hustle culture." For the second one, same as the above, the preposition "the" isn't necessary either.

Yes, but the sentence using “wavelength” is less clear on what is actually meant. And, to say “the cancel culture” is actually fine.

Yes. But no the in front of hustle.