Seems we have this debate every week. Different streamers and DACs are often optimized for different inputs and outputs, it depends on where the money is spent. I2S and DDCs do a great job of improving the sound of "affordable" DACs and streamers. For example: to this day I still use a Denafrips Pontus II with a Denafrips Iris DDC with a Bluesound Node 130.....and have for a couple of years, and it still works really well. That connection is I2S.
More expensive gear can have other connections optimized: AES/EBU or USB being 2; and in that case there may be no need for a DDC. But to dismiss any connection without trying is also incorrect.