Well, you are wrong
Your observation isn't completely wrong though as probably all chargers have buck/boost DC-DC conversion technology built in. However, you are completely missing the point. Just because something does DC-DC conversion it doesn't mean it is just a DC-DC converter. A DC-DC converter is strictly an unintelligent device converting between its input and output. The TP4056 is an IC, it is a microcontroller. There is also DC-DC conversion happening on the board, this is necessary for it to work, but the TP4056 brings all the logic to make charging a fully automated process.
That said you can charge lithium cells with any CCCV power source as a manual process. Most buck/boost converters and lab power supplies are suitable for the job. This works for single cells as well as serial configurations if the voltage is set correctly. However, obviously there is no balancing happening. This is something a smart charger, like a TP4056, would do for you. The TP4056 itself obviously wouldn't do it as it is set up for 1S, but you get the point. This category of device would do it in contrast to a simple DC-DC converter.
You can easily buy 10S smart chargers/balance chargers off the shelf than can handle 12V, 24V and 36V batteries. The RC folks will have you covered on that one, above that there are 48V chargers for ebikes, I think. However, these aren't usually balance chargers but merely AC-DC converters with CCCV.