OP, “…I’ve gathered that a streamer’s part is more than that.”
Absolutely! it is somewhat like the turntable / cartridge in the analog end in front of the Phono stage… so the streamer in front of DAC. Stand alone, purpose built streamers simply sound better.
Reasons, electrical and physical isolation, cacheing, I have had a dozen streamers over the last fifteen years and it doesn’t get high fidelity until you get to a high quality stand alone streamer. I now own the best streamer I have ever heard… it uses a battery to power the audio circuits and recharges while not in use, is built like a tank, and is far more reliable with sound even when my iPad will not refresh the screen. FYI, my streamer is the Aurender W20SE.
A few people have successfully upgraded every aspect of their Ethernet, router, MacBook… (as in shut down all processes and lots of fiddling) and gotten close… but it is a very difficult way to get nearly there.