UBI is a neo-liberal idea that does nothing to improve wages, it reinforces neoliberal narratives about accepting structural unemployment, accepting underemployment and provides a flawed definition of full employment that agrees with a “natural” rate of unemployment. For those of us on the left that see full employment as the goal then UBI does not achieve that. In effect it acts as a Government subsidy for private business.
Instead introduce a dignified income that applies to those unable to work or are retired and introduce a Job Guarantee, then full employment is achieved and those unable to work or who have retired have a worthwhile safety net.
UBI used to appeal to me, but the more I looked into it the less it appealed. It could create a permanent underclass of people unwilling to work and as a Socialist I believe everyone who can work should work and if that means the state creating work and then buying up all available labour to do that work then it is fine by me. In theory we could have a whole army of carer's for the aged through the job guarantee and whilst that may not be productive in itself, the wages spent can help the economy grow.
As we approach a neo-Malthusian world, then dignity for those of age becomes increasingly important and that has to be provided by economic growth and a Job guarantee can help growth far more than UBI.