if not for doublethink they wouldn't think at all

I won't deny that a portion of the population would definitely do this, but I don't think it's a majority. There's a nontrivial number of people who would stop working because they don't need to anymore, eg, working mom's with supportive spouses who work a menial job just to help cover the bills. They would definitely leave their work and spend time with kids and being a homemaker. Some would quit and do nothing because they're lazy. Sure.

I don't think that's the majority of the workforce. Many people, such as myself, do it mainly because they want to be productive and/or help people. Those like me, who are also happy with their employer (I presently am quite pleased with my boss/management), would not really do anything differently.

I think the root of what you're seeing is that if the basic needs were covered, people would quit bad jobs. Bluntly, there are a lot of bad jobs out there. I would venture a guess to say it's the majority. If someone hates their workplace but they need to make rent, they're more likely to stay with a bad job so they can have a place to live; these people, if their needs were met, would walk out in droves. That would be enough to move the needle over to a majority.

My argument from your statement can be rephrased as: if we met everyone's needs, they would have no reason to stay working at jobs they hate.

Which is very much true.

That's not what UBI tests have shown us in practice.

Anecdotally, a close friend of mine made enough to retire several years ago and now he just works a job he finds fulfilling instead of the highest paying one. IMHO humans instinctively want to contribute to the tribe.