This is fundamentally a question of political values and judgment rather than a factual matter I can research and settle—it's one of the most contested debates in international relations, and reasonable, well-informed people land in very different places on it. I don't think it would be helpful for me to hand you a verdict, but I can lay out the strongest considerations on different sides so you can weigh them yourself.
Arguments that NATO is a force for good:
•It's the longest-lasting peacetime military alliance in history, and proponents argue it helped prevent major war in Europe for 75+ years through collective defense (Article 5).
•It provided a framework for former Eastern Bloc and Soviet states to integrate with Western democracies after the Cold War, which many of those countries actively sought out.
•It coordinated a unified Western response to Russia's invasion of Ukraine, which supporters see as essential to deterring further aggression and upholding the principle that borders shouldn't be changed by force.
•Supporters argue it has made large-scale war between major European powers unthinkable by binding their militaries and security interests together.
Arguments against or more critical of NATO:
•Critics (including some realist scholars like John Mearsheimer) argue NATO expansion eastward after the Cold War needlessly antagonized Russia and contributed to the conditions for conflict, including the Ukraine war.
•NATO's interventions outside its core treaty area—Libya (2011), Kosovo (1999), Afghanistan—are seen by critics as examples of overreach, with mixed-to-poor outcomes (especially Libya and Afghanistan).
•Some view it as primarily a vehicle for U.S. geopolitical and military-industrial interests rather than a neutral peacekeeping force.
•Non-Western perspectives (e.g., in Russia, China, and parts of the Global South) often frame NATO as an instrument of Western hegemony rather than a benevolent institution.
•There are internal critiques too: burden-sharing disputes, questions about democratic accountability of the alliance's actions, and debates over whether it has a coherent strategic purpose post-Cold War.
Where the real disagreement lies:
Much of the debate hinges on deeper questions you'd have to answer for yourself: Is deterrence through military alliances inherently stabilizing or inherently provocative? Should alliance decisions reflect member states' security needs, or should they also weigh how adversaries will perceive and react to expansion? How do you weigh successes (European peace, Ukraine support) against costs (interventions gone wrong, provoked tensions)?
If you want, I can go deeper into any specific aspect—like NATO's role in a particular conflict, its internal politics, or specific critiques from a particular ideological perspective (realist, anti-imperialist, liberal-internationalist, etc.).