Interesting debate as I'm interested in language and it's allegedly one if my strengths.
I think the term "lived experience" is useful as it offers a shorthand insight into the potential impact of any experience, and most often it seems to be applied to traumatic experiences. The devil is indeed in the detail as every individuals experience is unique, however there will be commonalities that, for example, support services can identify, then build on and adapt to individuals.
I personally find it useful to know that someone I'm talking to has been identified as having "lived experience " of x, y or z because it means I can hopefully avoid sticking my foot in my mouth by waxing lyrical about things that I don't have experience of but can perhaps theorise about, and be miles off the mark. I think it helps inform sensitivity.
The arguments regarding the professional approach based on say, diagnosis and research are interesting, as I have "lived experience" of being dismissed and belittled by doctors and other professionals because my direct experience of events and situations doesn't fit their academic model and leads to conflict. We see it all the time on threads about trauma and extreme situations, the rush to tell people how they "should" think, feel or behave, rather than accepting that people react differently depending on a whole host of factors and need to work through and process things in a way that works for them to hopefully achieve a beneficial outcome.
There is a tendency to want life with all it's experiences to be formulaic, a tick box mentality if you will, but we're not robots or computers, there is constant adaptation and evolution, it's an almost fractal process in my mind.
Getting fixated on this phrase is a bit pointless, as it does serve a purpose. If you don't like it, fair enough, but the snippy comments about playing "top trumps" and "bending over backwards to avoid othering" in services are pretty petty and suggest some sort of ego wound.
Live (your experience) and let live (their experience) I say.