In any health intervention there can be the proponents who become zealous and unreasonable, holding people to too high a standard.
In the Keto/Carnivore space there is such excitement from finding a tool that works so well that advocates can become a bit annoying when they overshare with their friends and family.
Addictive personalities probably see quite a benefit in following a eating pattern strictly. These are the people who can not "moderate" temptation and must abstain to maintain their health goals. These are exactly the people who see the proper approach requiring strictness.
Not everyone is going to see the same benefits from the same intervention, and if someone is starting off relatively healthy their tolerances mean the tradeoff of strictness vs benefit isn't worth it.
For myself I've found that I can't hold people around me to the same standard I'm trying to keep myself at - I need the accountability for good outcomes, but that doesn't translate to other people.
At the end of the day all of these interventions are options, a menu of choices, that people can take or leave - I'm happy if I make that decision a informed one even if I wouldn't make the same choice.
My lifestyle right now is a big menu that wouldn't apply to most other people
Any one of these is a tall order - it's something I arrived at very slowly. I had to get significantly healthier before I even could tolerate the sauna regularly.