Our wifi chipset MT7921AUN has an open driver in the mainline. Of course wifi firmware is binary. But you can use the whole system without a wifi. Main idea is to make the platform open, so you don't need blobs to boot and use the system.
i can understand blob for radios: by only using a signed blob you are restricting a malicious user from abusing the radio.
However, the problem with binary blobs is that they are binary blobs: no sources, can't make changes, can't adapt them to work on a new system, can't audit them. Free folks have always argued that a computer will never be free if there are binary blobs in there
(well: the last part is not really true, there is always a way to have a custom firmware, or make an audit, but the manufacturer will do that only for elite customers. Not for open source folks.)