Well then, I apologize for not seeing your intent. For the record, I do understand that other people feel that fun. I simply have not ever felt it myself, ever, despite repeatedly trying (mostly in non-D&D contexts, to be clear.) Being beholden to the dice in that way makes me anxious and frustrated, rather than excited and curious as it does to those who like this stuff. That's no slight against anyone else; if anything, it's an admission of flaw on my part.
My only point in responding as I did is because of the logical leap from "getting a random character" to "it will make you get better at improv", and thus why I pointed out that the improvement is in no way guaranteed, whereas you legitimately can guarantee it by selection if you...select things you know you aren't good at improvising to force yourself to do it.
If that is irrelevant to your point, then there's no need to say anything further. My piece is said but irrelevant, and yours is done.