My thoughts on the creamy coffee.
Firstly, we don't need to add cream to our coffee. It is not mandatory. There are plenty of other ways to add (healthy) fats to your diet, the suggestion of adding cream is because is has fewer carbs than milk. Several milky coffees throughout the day and carbs can significantly add up. I'm ok with a small black coffee, but others can't stand it, hence the cream.
Coffee with butter and cream is very rich, and very full of calories. It may leave you not hungry for a proper meal. I look at @Goodiewhemper's delicious list of spinach, avocado, courgette, asparagus, cauliflower etc. and I think it would be a real pity to fill up on bullet-proof coffee and miss out on any of those.
The same with mct. People on some keto diets swear by it, but it is essentially a meal replacement and they are probably recording their macros (which is tedious) and looking for ways to up their fat without increasing protein, and while keeping their carbs very, very low.
The beauty of this woe (Thanks @BIWI ) is that by following the 10 rules we don't need to weigh or count carbs or calories. Trust the process, and make fine adjustments to suit. Also, and most important I think, is that this woe is long term healthy - much less processed food, lots of healthy veg, drinking lots of water, changing our tastes so we have less liking of sugar, sometimes adding in intermittent fasting.
However, there is also 'dirty' keto - full of bullet proof drinks, processed meats, fat bombs, artificial sweetners, keto bars etc. It will induce ketosis (not one of our targets necessarily) and those following it will burn fat and loose weight. But for me it wouldn't feel very sutainable and I don't think I could call it a healthy diet.
Having said all of that, sometimes in winter, if I've been out in the cold, I love a hot chocolate made with cream and coconut oil 