This is a normative/political question that reasonable people disagree on based on values, priorities, and interpretation of history—it's not something that can be resolved by looking up facts. That said, I can lay out the substantive considerations on different sides so you can weigh them yourself.
Arguments that NATO has been a force for good:
•Deterrence and collective defense: NATO's Article 5 mutual defense clause has arguably prevented major interstate war in Europe for over 75 years by making aggression against any member costly for all potential aggressors.
•Stabilizing post-Cold War Europe: NATO expansion is credited by supporters with helping integrate former Soviet-bloc countries into a stable, democratic, prosperous order, reducing the risk of the kind of great-power conflict that devastated Europe twice in the 20th century.
•Crisis response and humanitarian roles: NATO has conducted disaster relief, counter-piracy missions, and interventions framed as preventing atrocities (e.g., Kosovo in 1999, though this is itself contested—see below).
•Support for Ukraine: Since 2022, NATO members have coordinated substantial military and economic aid to Ukraine, which supporters see as defending the principle that borders shouldn't be changed by force.
Arguments critical of NATO's role:
•Provocation thesis: Some analysts and realist scholars (e.g., John Mearsheimer) argue NATO's eastward expansion after the Cold War needlessly antagonized Russia and contributed to the conditions for the 2008 Georgia war and 2014/2022 Ukraine conflicts—though this view is contested by others who argue it removes agency from Russian decision-making.
•Interventions with mixed or negative outcomes: The 2011 Libya intervention, authorized under a UN mandate to protect civilians, is widely criticized (including by some NATO members' own officials) for exceeding that mandate and contributing to state collapse and prolonged chaos in Libya.
•Legitimacy and unilateralism concerns: The 1999 Kosovo intervention was conducted without UN Security Council authorization, raising ongoing debates about international law and precedent-setting for other powers to bypass the UN.
•Democratic accountability and burden-sharing disputes: Critics point to tensions over unequal defense spending among members and question whether decisions to intervene reflect member states' publics or elite/institutional momentum.
•Alliance as bloc politics: Some view military alliances generally as perpetuating a zero-sum, bloc-based international order rather than fostering genuine collective security for all states.
My take: Whether NATO is "good" depends heavily on which values you prioritize (state sovereignty vs. self-determination, non-intervention vs. humanitarian protection, deterrence vs. provocation dynamics) and which historical counterfactuals you find plausible (would Europe have been more or less stable without it? would Russia have behaved differently absent expansion?). These are genuinely contested among serious historians, IR scholars, and policymakers—not questions with a settled empirical answer.
If you want, I can go deeper into any specific episode (Kosovo, Libya, the Ukraine war, expansion debates) where there's more concrete historical detail to examine.