Many phones/chargers with propietary protocols are also equipped with USB PD compatibility. For example, you can pick up some random Xiaomi phone labelled at 90W and expect it to charge at more than 20W with USB PD, or even ~90W on some vivo models.

I don't see why the best charger is the old feature phone's charger - the point in fast charging is that you don't have to wait too long if in a hurry. That charger is the "best" if only you have almost unlimited time to charge, like during the night.