Doesn't matter what you're making, none of it is good for you.* Some substances are much worse than others, but at the end of the day, whether that substance is crack, cannabis, or nicotine, you're still inhaling a foreign substance.
* unless part of a medical treatment regimen prescribed by a medical professional
If your doctor prescribes you something for smoking, get a new doctor. That said, crack is the worst for your teeth due to clenching, and tobacco is the worst for pretty much everything else imaginable. Smoking generally is the unhealthiest habit people have, but it's specifically due to inhaling the free radicals produced by combustion, not "a foreign substance" (we are all continuously breathing foreign substances). If you were just able to take out the combustion part somehow, you could- ah shit they're already marketing it to kids
Smokeless tobacco has been around for centuries. Snuff (and I don't mean Snus) the snorting route is actually relatively safe. One or two instances of cancer in centuries.
I mean to say that for some medical ailments, the treatment is smoking. The treatment for smoking addiction can involve vapes. The treatment for many mental disorders can involve cannabis. edit: I'm wrong about this
You're right that it's not the foreignness of the substances that is the cause of harm, but rather the nature of the substance and the amount consumed (which is usually a substantially large dose compared to others)
Meth is expensive but gas station thc vapes are also bad for you for a fraction of the cost. My favorite flavor is nitric acid. Fresh out of a amateur chemistry project in some barn.