Macronutrients are not what makes a food healthy. In particular, high-protein does not make a food healthy. By that reasoning a lot of fast food could be considered insanely healthy, but it’s not. That’s just our downright shitty levels of education surrounding nutrition.

What actually makes a food healthy depends on a lot of different factors, but a common one and relatively reliable standard bearer is whether it is “nutritious”. When a food is nutritious or nutrient dense, it is micronutrient dense. This includes things like spinach and beans and seeds and broccoli and all of the other foods that your parents made you eat. Micronutrient poor foods are ones that have relatively few micronutrients, but usually are relatively calorie rich. This includes things like mozzarella sticks, wonderbread, fruit gushers, heavy cream, twinkies, and so on. We do need macronutrients, but virtually anyone who gets enough energy (calories) from food also gets enough of them, except in specific cases like being a professional athlete. The athlete wouldn’t die of protein deprivation if they didn’t pay attention to their intake, but it would make it harder for them to perform well.

So no, chicken is not, by any standard, “really nutritious and healthy”. It’s not completely devoid of nutrients - it’s relatively rich in phosphorus and selenium if you eat it on its own, for example, but it’s far from what anyone would consider nutritious. It’s somewhere in between fried mars bars and spinach.