I work in a restaurant and as such have a particular passionfor cooking and as such I have many a gadget in my home kitchen and my ninja is one. It has its place, but the only function I find irreplaceable is the pressure cooker.
The otherfunctions can generally be replicated in my oven or by other means. Amd i feel that i get a better result with traditional methods. The biggest pro for me is the speed it heats and therefore cooks. Definitely faster than an oven, but the capacity can be limiting. 9 time out of 10 i choose to cook with more traditional means.
I fear many airfryers in the uk and left to collect dust, or mearly used to cook the likes of fish fingers, chicken nuggets and chips (Fries for you Americans😁)