10 years and tens of millions of users means insufficiently abundant evidence?
It's like the fearmongering around MDMA, which claims that there will be delayed harmful effects from meddling with your brain chemistry, but hundreds of millions of users and decades later where is the widespread harm? Arguably it proves that it's one of the safest drugs on earth.
Of course controlled studies are rigorous, but widespread use must also lead to widespread harm if it exists. There may be hidden harm because it's a small effect on a large population or only harms a small population, but that just means it's relatively safe.
It’s closer to thirty years in terms of initial cannabis vaporisation with more significant usage in the last twenty at least. Unless you are referring to the newer vape pen style which may be closer to a decade.
Not sure about lung cancer, but we know enough about the negative health impact of air pollution that a little common sense should tell us that putting random garbage in your lungs is unlikely to be good for you.