Well, it's not easy. I like that you worded it, "only" about winning. Because, yes, winning is something a coach should care about. If you didn't try to win, it wouldn't be competition, right? But there is a subtle, yet HUGE difference between trying to teach, inspire, develop, train, and mold players so that they can win in the long run, vs. being only results oriented, and trying to put players together to win right now.
To answer your question, the only way is to meet a lot of coaches, interview them, ask questions, be curious about their style and methods and philosphy, and then observe what they actually do: Do they just talk the talk? Or do they practice what they preach? Ask other parents. In particular, seek out parents of older players, or HS players, or especially college players and ask them about their experience and who they thought were impactful coaches.
The best coaches my daughter played for in both youth & college won a lot of games. But their approach wasn't so much fixated on the wins as much as how to get the players prepared to win. By contrast, she also had two or three who were the opposite. Interestingly, those coaches had short term success followed by player turn over and long term failure. Two of them quit coaching as well. The players that stuck with those "win-first" coaches also suffered in their careers and either quit or did not reach their goals and potential.
This is not to diminish the earlier comment that players should be in charge of their own development. That is true also. But it sure makes that journey more enjoyable if you have a great coach to help along the way.