I think healthy for whom? I would say for example marijuana is no worse than some prescription medicines kids are given. I will not name these for political reasons but some of these medications have been shown to alter the brain with possible unknown long term effects. We also know marijuana isn't exactly a vitamin but it's not what I would consider unhealthy either.
I would say compared to caffeine, THC is healthier. As you can have health problems from excessive caffeine including insulin resistance, higher blood pressure (increased risks). At the same time I would not say marijuana is as beneficial as kale. Kale is one of the most nutrient dense foods there is.
So I would say no we cannot compare marijuana to alcohol. Alcohol has no medical use cases that I know of and doesn't benefit human health at all from what I can see. Marijuana has some marginal benefit to human health but the long term impact remains unknown. What we do know is it's not good for children but a lot of stuff which is good for the aging population is bad for the growing population.
I agree we need a larger data set to analyze.