My most common jq usage is to copy and paste some json into quotes to make it easier to read. My second most common action is to chain curl and jq together. A replacement for jq that doesn’t use stdin is literally useless to me.
That’s a cumbersome extra step for unclear benefit.
Yes, q is supposedly faster than jq. But it is exceedingly rare for me to ever have any performance problems with jq, especially since it’s essentially a one off utility I use occasionally, not as part of the hot loop of any workflow where performance matters.