This is a genuinely contested question where reasonable people disagree based on different values and readings of history. Let me lay out the actual debate rather than pick a side for you.
The case for NATO as beneficial:
•Provided collective defense that arguably deterred Soviet aggression during the Cold War
•Democratic member states, unlike Warsaw Pact
•Article 5 mutual defense created stability in Western Europe post-WWII
•Support for Ukraine is framed as defending a democracy against unprovoked invasion
•Enabled European integration/peace by reducing security competition among European states
Critiques and concerns:
•Post-Cold War expansion eastward is seen by critics (including some realist scholars like Mearsheimer) as needlessly antagonizing Russia and contributing to current tensions
•Interventions outside the North Atlantic area—Libya (2011) in particular—are criticized as regime-change operations that left chaos behind, exceeding NATO's defensive mandate
•Yugoslavia bombing (1999) remains controversial—stopped ethnic cleansing according to supporters, but bypassed UN Security Council and killed civilians according to critics
•Some argue it locks the US into European security commitments that don't serve American interests, or gives European states less incentive to build independent defense capacity
•Question of accountability—decisions made by an alliance rather than through clearer democratic mechanisms in each country
Where the real disagreement lies:
Much of this hinges on unresolvable counterfactuals—would Russia have invaded Ukraine without NATO expansion? Would Gaddafi's fall have happened anyway? People's answers here correlate heavily with prior political commitments (realism vs. liberal internationalism, views on US foreign policy generally, etc.)
I'd rather help you think through specific aspects—like the Ukraine situation, the expansion debate, or a particular intervention—than deliver a verdict on "good or bad" as a whole. What's driving the question for you?