This is why basic income experiments like YC Research, the Ontario one, the finished Namibia one etc are all important. We need to see what happens in different cultures, in different communities, in different economies when we give un-earned income to people with no strings attached. We need to see what will happen.
You can absolutely bet if you give enough people free money, there will be ones that opt to do nothing but sit around playing their ninplaybox consuming their drug of choice. You can absolutely bet that some will use it to make positive life changes though like improving their diet or health care, seeking training, starting a side-hustle. We need to do these experiments for years and years in many areas in many populations to see though what exactly will happen.
I imagine if you took groups from the same state here in the US and gave those in a rural community money they're going to behave differently than someone living in an urban or downtown setting. Different if one group is in an economically depressed community and one is in a community full of healthy local businesses and corporate jobs.
I wouldn't call it a myth, I'd call it a theory with inadequate evidence to support or refute it.