No Stupid Questions

I think it's more about what we mean by "failure". That probably sounds silly so I'll lean into the coffee shop example. Imagine if a coffee shop was successful, but then something beyond the control of the owner happened to make it no longer profitable. In this world, the business may have failed, but it may not be accurate to say the business owner has failed. Or maybe the business becoming less profitable is directly because of the owner, who may be taking less time being active in managing things, perhaps because of other things in their life taking their attention. Again, there's a sense in which they're a failure here, but in practice, it may just be that their life circumstances and priorities have changed. It might be failure with respect to the coffee shop, but I don't think that's failure with respect to their life. Even if the reason the coffee shop shut was because they didn't anticipate how stressful it would be and they regret ever attempting this endeavour, I think that considering this a failure risks not acknowledging the growth and learning involved.

I liked the marriage example because I used to be engaged to someone who I spent the first chunk of my adult life with. We broke up because we had grown into people who were no longer compatible, and it was a moderately messy breakup because we didn't want to acknowledge that fact. I think that in this, and many other relationships I've seen, people's aversion to "failure" causes them to stick it out for far too long in bad relationships, which ironically leads to messier breakups and a situation which is much more clearly a failure.

I think the big problem that OP attempts to highlight is an overly binary view of success. Like with the coffee shop thing, I posed personal and commercial as two different axes of success, and I think there could be more. It encourages us to attempt to gauge the "objective" value of things that are incompatible with that kind of quantification — the bit of your comment about longer lasting friendships is something I actively disagree with you on. Some of my most cherished friendships are ones that belong to the past and it wasn't because of lack of importance why they stopped because active: most of the time, it was just that we had become different people, in different circumstances, such that our lives were no longer compatible. There is still great love and care that exists between us, but as active friends, things have changed. In a way, these friendships feel like they were actively successful, because of how instrumental they were in helping me grow to the person I am now. I don't think failure is a useful lens to view outgrowing something

Edit: I worry I have come across as overly argumentative, so I want to clarify pre-emptively that whilst there are aspects of your comment that I disagree with, I appreciate the time you spent writing it because the ways in which I disagreed was thought provoking. The primary reason I wrote my response was more an exercise in articulating myself than an attempt to sway you — this subject area is subjective and nuanced enough that agreeing to disagree is more than fine.