There are a bunch of ways to describe the quality of a product you want to sell; here's three of them.
- Are most of the engineers who worked on it proud of their work?
- Are people likely to pay for it?
- Are people who paid for it likely to recommend it to others?
But I'd argue these three are a hierarchy; you can't have one, sustainably, without accomplishing the others before it. If people don't use your product, you're not going to get them to recommend it. And if your engineers aren't proud of the work... that's a bad, bad sign, and unless you know all the reasons, it's dangerous to move forward blindly.
If your engineers aren't proud of their work, they won't work as hard, they won't work at the same quality, and they'll leave the team sooner instead of later, all other things equal. If your product has any complexity - almost all do! - higher-than-normal attrition of engineers is just about the worst thing you can have happen; after long enough on any product, engineers have knowledge in their heads that's more costly to replace than their actual paychecks.
Most of the reasons an engineer lacks pride in their work fall into:
- They don't really understand the product. ("Who buys this? Reality show contestants?")
- They don't think the product is good for the users. ("This is a hot mess, and I don't want my name on it.")
- They're afraid of the technical debt that was accrued. (It's hard to fix bugs, it's hard to add functionality, and/or it's hard to scale.)