An oven (even small, countertop one like it's shown here) has much bigger volume than standard air fryer. From my experience ovens hold low temperatures much better than air fryer does. An oven also gives you more options, because you can not only have convection setting (which literally makes it air fryer over), but you also can have inside stuff like grill, "keep warm" setting, "rise" setting for dough proofing or even whole rotisserie appliance inside.
So, an air fryer is basically small convection oven made for purpose of... well, air frying, aka convection roasting small potions of food and reheating stuff, that's supposed to be crispy. It's good basically only at this 2 things, but it's definitely superior at those functions over an oven, cause it's faster, more effective and in some cases more energy efficient. It's perfect for someone, who's living alone, doesn't have much interest in cooking, but still want to eat cheaper and healthier meals, than you can get from delivery.
An oven on the other hand is more universal piece of equipment, suited for someone, who's more interested in cooking. You can not only air fry in it, but you can grill (and by grill I mean broil), roast (even slow roast), bake and dehydrate food. It also can have multiple different helping options, like I mentioned earlier. With bigger volume comes also ability to make food for more people at once. It's also overall less energy efficient and and less effective at convection roasting than air fryer is (comparing appliances at similar price range).
Tl;dr - an air fryer is by design excellent at two things only, is highly limited by it's size and is fairly efficient, suited for 1-2 people max, while an oven is good at multiple things, good for someone who likes to cook and need more options than just convection roasting, it's bigger size allows you to cook more food at the same time, but it's less efficient.
What can you do in an oven, that you can't in an air fryer? You can bake cakes and other desserts, you can slow roast a piece of meat, you can bake pizzas from scratch and not only reheat it, you can make casseroles and other baked pasta dishes, you can make dishes, that requires you earlier to use pans, which then you can inset to the oven (i.e. reverse sear method, frittata, quiche), you can grill (broil) stuff in there to achieve char flavors, etc, etc.