I love USB-C for charging and data and display. But it does not replace 3.5mm. Aside from the things mentioned so far in the comments here, a fundamental problem is that now headphones need DACs in them.
The engineering specification states that an analog headset shall not use a USB-C plug instead of a 3.5 mm plug. In other words, headsets with a USB-C plug should always support digital audio (and optionally the accessory mode)