If you DM 5e, not only are you poisoning yourself, but you are poisoning people around you.
The position that it feels like some hope to reach - and I hope I am mistaken - is that MMI and 5e are essentially synonomous. It's hard to hold a conversation in good faith on those terms (as others have pointed out.)
Absolutely not. See above.
MMI is a likely (but not guaranteed) consequence of some of the design choices and components present in 5e. It is also, as I have taken pains to demonstrate, a likely (but not guaranteed) consequence of some of the design choices and components present in 3e, a system which is much more rules-heavy and theoretically less "DM dependent" than 5e is, even though the two share numerous similarities.
It is these design elements I want to point to, analyze, and address. I have no belief that 5e is "equivalent" to MMI, and frankly find the idea ridiculous. Instead, I think it was made in such a way that it has a very high innate susceptibility to such DM behavior, and that it offers few tools to address this issue. As a result, people who use it are liable to either encounter issues, or resort to undesirable methods to self-treat, which can lead to further issues.
Obviously, my preference is a system that does not do these things. A system that includes active and passive safeguards and tries not to undercut natural defenses against this type of dysfunction. That cannot happen with 5e, in part because it already exists and in part because the developers have been reluctant to make any changes to its core (though the upcoming 6e/5.5e/5.1e/whatever seems to change this stance.) Since no change to the actual system itself is possible, identifying risk factors ("carcinogens") and ways they can be managed, mitigated, or preempted is the only remaining recourse.
Of course, as a consequence of this management, mitigation, or preemption, there will almost surely be some expectation that both players and DMs abide by some kind of binding commitment. This may be interpreted as "taking away DM power" or the like, but I find that to be essentially the same as dismissing MMI as an issue of any kind in the first place. Another consequence, however, may be the conclusion that some people just aren't a good fit for DMing 5e, or perhaps even just playing it. If the game leans so heavily on social contract and continuous forthright communication, those who struggle with communication or who prefer to keep players in the dark may simply be bad fits for 5e DMing, though few people are likely to appreciate being told that.
D&D contains ‘carcinogens’ isn’t any better.
What else am I supposed to say? "Oh no, nothing whatsoever is wrong with 5e, it is absolutely perfect in every respect, and all these issues with DMs feeling overwhelmed and under-supported and with players feeling frustrated and subject to whim and fancy are totally unforeseeable, unpredictable faults that just randomly happen sometimes!"
Carcinogens are things which increase the likelihood that a person will suffer a dysfunction of cellular replication leading to problems. I believe there are rules elements in
many different games which cause a heightened likelihood of MMI, a dysfunction of authority regulation leading to problems. 5e happens to have several of these. That doesn't make it some horrible awful assault on human decency.
Alcoholic beverages are known to be carcinogenic to some degree. This fact does not mean I want to crap on people who drink them. (Far from it. I am one myself, albeit only rarely.)