There isn't any direct relation between ownership and overprocessing. What I believe you look for is limiting overprocessing in a way that doesn't harm ownership and not a balance between one and the other. Actually, I'd say that you just look for a way to just limit overprocessing. Period.
It seems that one thing you miss in your team is common understanding of your goals or, which would be even worse, common goals at all. I mean, you, team members and team leader should all understand where you are heading and what is at the end. You should all share the same view of what is the outcome of a the project and of what quality it is. And then, what is needed to get there.
At the end of such discussion you may end up either agreeing that pursuing perfection is something you want, but you will also be aware that it doesn't come without cost. Another outcome, and the one you expect, is that you set the bar too high and you aren't willing to pay such high price within this project.
Either way everyone involved would understand what the goal is and what is needed to achieve it. Bearing that in mind everyone in the team should find it easier to fine tune their activities in a way which brings you closer to the goal.
It would be even easier considering that you work with people who have the sense of ownership. As long as they, as a group, own the goal their actions will likely adjust their behavior in a proper way.
Think of it this way: let's say that the goal is to have the first version of the app live before some date because otherwise something bad happens (your app doesn't follow law changes, a competitor gains the attention of early followers or whatever). If everyone in the team understands this, they will also understand (and see) that pursuing perfection with one of many features simply increase the risk of not making it on time. If such situation happens for the first time its impact may be ignored but delay built every time something similar happens would be hard to accept by anyone. I assume understanding this would simply change the attitude toward overprocessing.