It precisely doesn't have anything to do with the fact that workers must exist, this would give people leverage to decide if they want or not to work. In this case most people will rather do what type of work they prefer rather than to be coerced by our current "free market" to chose any job as long as it pays.

If workers exist, then there is a working class, which is not the leisure class, and therefore fails to fulfill "no class but the leisure class."

I did, I mentioned automation, and you said that this has happened all throughout capitalism and that it's merely a way to increase worker throughput (and I wasn't paying enough attention when replying to this so I didn't give the right answer, sorry). It's true that in the past automation was only used to make things more efficient and cheaper without displacing workers, but this time there are AIs developed that can do much more than specific tasks, and that can learn by themselves: https://youtube.com/watch?v=7Pq-S557XQU[1] , so it is possible that in the next decade we could see an increase in the displacement of workers. This would create the "leisure class", but it would be a class without disposable money, so to solve that an universal basic income could be introduced. At first it could be paid off by raising taxes (depending on which country we're talking about) or removing some bureaucratic, means-tested forms of welfare (which are highly inefficient), to assure a decent standard of living, but this would require people who need more than that to still take a job (which will not remove their basic income). Later on to give out a higher basic income we could tax factories that produce goods with automation. Hope this makes my argument clearer.

That's not the leisure class, that's the lumpenproletariat.