I get what you are saying but bad and good are too open ended in their definition.

I have a saying I use that is kinda similar and may define your point a bit better;

“Regret can turn into wisdom over time”

It’s not an always thing, but if you can reflect on your regrets you can gain wisdom from your mistakes to better yourself going forward.

No, a bad experience is bad. It cannot be good. But it can be useful, though.

Yeah, no - tell that to someone forced into a corner and assaulted. For a “bad experience” to have something to learn from it, one has to have made a poor choice that lead to it first. Sometimes in life, bad experiences are just random bad luck.

i vote wise this time. not spectacular, but good, and a wisdom which is always healthy to hear and thus reinforce. It isnt the experience but how one let’s it shape them.