Just wondering.

The polite padding does have meaning. It specifies the person is ONLY wondering and not also judging, or accussing, or assuming. That is to say, just is very explicitly specifying that wondering is to be understood as a pure wondering, in its most literal definition with any emotional or social or situational valences stripped.

"I just want to..."

Strip just and you remove a sense of exclusivity

"I want to..." Does not imply a lack of interest in other things

Exchange it in most cases though and you extend the exclusivity to a global sense

"I only/specifically/singularly want to..."

Gives a sense of unique universal purpose rather than a simple specific task of the moment

Your last paragraph concedes its usefulness 🤔

What is just? What is fair? What is right? What is good?