Actually, that is not entirely true. Nicotine doesn't have a positive effect on everything. ONly some things. It will not be good for PAD (peripheral artery disease in legs for instance), Raynaud's, any kind of venous insufficiency (your ankles swell after sitting a long time, etc.) and a few other things that people get when they are over 50.
I think we have to be careful not to make sweeping statements. Vaping has always been harm reduction, not harm free.
It is true that in order to increase the harm reduction part, there are a number of things vapers can do, and this has been discussed ad nauseum across hundreds of topics. (avoid certain chemicals in eliquid and also dyes, food colorings, etc. ), try not to vape 30ml+ per day (try to put as little extra "stuff" into your already-damaged-from-smoking lungs), try to avoid over-flavoring, try to avoid burnt hits, fake sweetners, etc.
What I've noticed is that there is a balancing act between being in total denial (wanting too desperately to have vaping be the "magic bullet" when it really isn't, it is only harm reduction and better than smoking) ------- I think those who refuse to recognize that that harm reduction doesn't mean harm free are wanting more than can be offered.
sometimes, the defense of vaping borders on the ridiculous, because some of the things I just mentioned are pretty much "common sense".......and many vapers are already incorporating a form of "less is more" into their vaping behavior.