"But it loses key ports – including the SD card port and the old Thunderbolt port – which people have typically used to transfer video and audio files and attach peripherals."
Do you know anyone who attaches peripherals natively to the old Thunderbolt port, as opposed to via an adapter?
No, nor do I. So you are living the dongle life either way, with the big differences being the availability of multifunction dongles for USB-C, and the fact that native peripherals will doubtless become more available than they ever were for the old port.
Anyway, anyone who thought Apple would do anything else must have been living in a cave for the last 3 years. By far the most interesting change is them removing the proprietary Lightning port from the iPad Pro: since that port collects a license fee from every peripheral made for it, and at the same time ensures that those peripherals remain incompatible with other manufacturers' products, I found Apple adopting an open standard there (even if it is the same as their laptops use) genuinely surprising.