Interesting, but about when was it that you personally had in mind as being "the past" when claiming that There is actually more healthy food available than in the past? And since I'll be asking next in any case, what are these foods you believe are more healthy, and what leads you to believe that they are now more available?
If ALL you ate were meat, cheese, and chicken, you would not gain weight. Obviously, whatever works for you is fine for you, but this would be a tad out in left field as advice for others.
Yes, I am well aware of it, and ketosis is not an illness but a chemical state. Ketogenesis is the process of converting stored body fat to ketones that are then burned for energy rather than the carbohydrate-based glucose that would otherwise be available in the bloodstream if one were not on a low-carbohydrate diet. Short of liposuction, there simply is no better means of reducing stored body fat than ketogenesis, so yes, it is a very good solution to a weight problem.
Yes, I would guess that I am quite a bit more conversant on this topic than what you seem to think. You will of course not get the same quality of protein from a vegan or vegetarian diet, and to allow your body to build the bank of complete proteins that it requires to maintain health, you will need to eat a range of veggie protein sources throughout the day. Veggie diets typically do provide plenty of fiber, vitamin C, and unsaturated fats, but the more strict the vegetarian limits become, the more you will have to worry about getting sufficient calcium, vitamins D and B-12, omega-3's, iron, and zinc. Supplements to reinforce those are often a good idea, but given all that, there is certainly no requirement that one must "eat meat or die".