Eleanorrigby:
i think i understand what you're trying to say in your 'pros' paragraph. sometimes it's important to tell someone straight up if they're in the wrong in a specific situation, and help them brainstorm solutions. it's how we grow, and how we help the people around us grow. if we surround ourselves with people who won't encourage us to be the best version of ourself, even if we don't necessarily want to hear it, we'll remain stagnant.
HOWEVER- the vast majority of the time, this is NOT the category that 'unsolicited advice' falls in.
unsolicited advice is usually not appreciated because assuming you know a person or their situation better than them is, quite frankly, incredibly condescending. in my opinion, if someone isn't asking you for advice, and is getting upset when you give it, there's probably a reason. maybe they already know how to handle it, maybe they've tried the advice already, or maybe they just need a friend to listen to them for a bit.
sometimes, the best thing we can learn to do in life is learn we don't need to be 'right' all the time. if someone says the advice that's given is unsolicited, or is upset by it, just apologize and move on. if it's someone we care about, we should have enough respect for them to trust that they know whether or not they 'need' advice or not.
Im considering "(uncolicited) advice" to strictly be what you'd consider "valid". For example, is the advice given on point, relative to what the reciever is troubled with?
If you just want to vent, for example, for something that you know how to solve, but nevertheless gets you frustrated, the problem is... how the problem is articulated by someone who might attempt to give advice. That is, its not a matter of finding a solution (since you already know that), but something else. In this case, its actually something i can't quite pin down really, but its something within the domain "I need to socialize".
Another criteria is, is the reciever of the advice already conciously aware of the information given? If yes, thats of course another case the advice is not "valid" (=helpful) That case shouldn't be difficult to manage. The reciever should just state that. It removes the need for you to guess if they already know what you told them.
You are basically right when you say the vast majority this is not the category that "uncoliced advice" falls in. I think thats also a problem because it makes it harder for us to identify errors.
With the case where the reciever is already aware, for example, the error is not that the advice given was not apropriate, because thats a valid logical consequence of missjudging. So the error made is not on somebody's behavior, but on somebody's thinking process.
Also, i find it interesting to try and map out all of these situations that result in unhelpful "uncolicited advice" . Categories like, self-serving, missjudgements, all these are valid possibilities.