USB-C is just a connector. Some of the devices using that connector only support USB 2.0 signaling over that connector, so USB-C does not imply complete superiority over FireWire.
What protocols are commonly implemented by Intel host chipsets which support the USB-C connector, e.g. on a 2017 laptop?
Thunderbolt 3, DisplayPort, USB 1.1-3.1, FireWire, HDMI, MHL, analog audio, power delivery
FireWire? That would have been a good addition to the article. Hopefully that will allow older FireWire devices to be used with a USB-C-to-Firewire adapter.
A cursory google search did not reveal any USB-C to FireWire adapters; there are Thunderbolt 3 to 2 adapters (Thunderbolt 3 is basically USB-C version of Thunderbolt 2 which is Mini DisplayPort) and there are Thunderbolt 2 to FireWire adapters, so that combo may work
Using a TB3 -> TB2 adapter and a TB2 -> FW800 adapter definitely works on Apple hardware with every FireWire device I've tested (hard drives, cameras, and audio gear)
I've not seen any simple adaptors, but OWC's Thunderbolt 3 dock includes a FireWire 800 port.
Do you have an example of a device that only uses USB 2.0 over a USB-C connector? I wasn't aware of such a thing.
All phones with type c
Not true. My phone, a Pixel, has USB 3.1 Gen 1. The Galaxy S8 is also USB 3.1 but I'm unable to find which gen it is from five minutes' Googling.
Some smartphones.
Older ones maybe. The latest generations of flagship phones use USB 3.1 over Type-C.