Air fryers are great but I wouldn't recommend buying an air fryer by itself. I've had a standalone air fryer and I didn't think it had enough uses to justify the cupboard space. If you want an air fryer, best to buy a device that also air fries. For example:
Ninja Foodi (Pressure Cooker + Air Fryer)
Ninja Foodi Oven (Toaster Oven + Air Fryer)
Ninja Foodi Grill (Indoor Grill + Air Fryer)
I own the Foodi and the Foodi Oven, and I personally use the oven a lot. For example, yesterday morning my wife toasted a bagel for her and a waffle for our daughter for breakfast. For lunch, I baked some chicken thighs and my wife made english muffin pizzas for her and my daughter. For dinner, I cooked burgers out on the grill, and my wife cut potato wedges and air fried them in french fries. The oven is substantially bigger than a normal toaster oven, but it still works in my kitchen space. (It also folds up and out of the way, but we never do that.)
As other people have said, it's real strength is heating frozen foods and reheating leftovers. Leftover pizza from the air fryer is just a hair away from being just as good as eating it fresh. I mentioned making chicken and french fries, and I've even made a grilled cheese sandwich in one. (It was good, but different from one made in a pan and it wasn't any faster or easier.)
Hope this helps.