Air Fryers really are game changers. I think they should have been called something else, as people seem to think that if they don't fry a lot they won't use one, but in fact they do so much more than fry. They use much less power than an oven, and keep the kitchen cleaner than cooking conventionally. They crisp food without adding fat (or sometimes a light spray of olive oil), so they are healthier, too.
I have a Ninja one and a Tower one with shelves, which I use for different purposes. My microwave also has an Air Fry function, and this morning I used it to make sausage and bacon rolls for my son and DIL, who are staying here this weekend.
It used one 'pan', there is no grill or hob to clean, and no grease in the kitchen. I put the sausages in first (no added fat) then added the bacon after 10 mins so it all came out together ready to make up the sandwiches. I was up first, so I got it going and left it to get on with it while I had my morning cuppa. Much easier and more efficient than either a frying pan or grill, and I just had to wipe the inside of the microwave when I'd finished.
Most gadgets aren't 'necessary', but they can give more options, and cut down on mess. The microwave is on the worktop anyway, and the Ninja lives in a drawer, although I am planning to move it to the boot room where I can leave it out.
I use the Instant Pot for pulses, pasta and soup, amongst other things, the slow cooker for casseroles in winter, the microwave for heating leftovers, the GF grill for grilled veg, toasted sandwiches and more, Air Fryers for roasting chickens, cooking chips, making Yorkshire puds, making cakes - in fact I only use the oven when I'm cooking for a crowd, or if I'm doing more than one pizza. I still use the hob to boil and simmer things, and to fry onions etc, but realistically I could manage without the oven.