Like any way of eating, it is possible to eat both healthily and unhealthily under an umbrella label such as 'plant based' or 'carnivore'.
A diet of processed meats 24/7/365 is not going to be anywhere near as healthy as one of muscle and organ, with range and variety, though there are people out there who have eaten ribeye steak 2 or 3 times a day for decades, and are in fantastic health.
My own experience of 3 years or carnivore is that yes, it can be very good for me, and carried a range of benefits.
I have malabsorption issues, and need to supplement some mins and vits because I don't absorb enough of them whatever diet I am on, so I will always need to supplement no matter what I am eating (folate, B12, vit D3 and manganese seem to be the worst). The same does not apply to other ppl.
In addition, many, many ppl on omnivorous diets need to supplement, including anyone on an only veg (vegan) diet. So the supplement discussion is obsolete. Especially the Vit C question. A quick google will establish that without carbs in the diet, the requirement for Vit C plummets and different chemical pathways are triggered, making Vit C in the diet either unnecessary, or easily fulfilled by liver, muscle meat or roe.
There are incredible superfoods such as fish roe and chicken, ox, pig and liver, brawn and kidney, which offer better nutrition than anything in the plant world. So no need for veg in that respect. Various carnivore websites examine this info in detail, if you go looking for it.
The reason I gave up on veg was because the fibre was doing terrible things to me. So no, my body does better on zero or very little fibre than the highly questionable orthodox advice on recommended fibre intake.
There is a huge (and growing) community of carnivores across the world, from top performing athletes to those who adopt the way of life to avoid a specific health condition (such as arthritis, or in my case gut issues). Again, Google will find facebook and individual websites, podcasts, and blogs showing just how successful carnivore can be.