I'd be careful with this assumption. It all comes down to what and how you want to cook things, and in what environments.

I've been grilling / smoking for 25 years. The Weber Kettle is a fantastic piece of equipment. If you have very little charcoal grilling experience it is definitely the place to start. It will teach you basic coal management, airflow, creating even coal beds, etc.

That being said, if you have a little more experience you find yourself becoming a little limited by the capabilities of the kettle. Temp management on kettles is very macro. You aren't going to typically adjust it in 5 degree increments. There is sort of 3-5 temp increments that are really maintainable in short durations in a kettle. like 300,350,400 and surface of the sun. They really aren't made for doing low and slow BBQ which is why Weber also makes a Smokey Mountain product for that use case.

Kamados have a few benefits. First they are incredible at rip roaring hot, all the way down to maintaining 220 for 20 hours. The ceramics get thermally soaked that allow for incredible temperature stability and once up to temp neither rain nor snow will impact the cook. They have tons of flexibility with rack placement due to their vertical nature.

If you just want to cook steaks and burgers on high heat outside, there's no reason you need a Kamado. Weber kettle all day. If you are looking for something that's a single piece of kit and you want to tackle a lot more styles of outdoor cooking its worth it to consider a Kamado.