Purpose of this IC in USB 3.0 Hub
You need the mux to handle the case of plugging in the USB-C cable in either direction. The super speed pin pairs are only wired to one side of the connector, so your circuitry must figure out which way it is plugged in and set the multiplexer accordingly.
Another mux you can use is the OnSemi NL3HS3124A https://www.onsemi.com/pub/Collateral/NL3HS3124A-D.PDF
If you don't need super speed (3.0) then you can ignore those pins and don't need the mux, but you'll only get USB2.0 data rates.