No it didn't. The ACA slowed cost growth, which was already skyrocketing by the time it passed.
in the 2000s (pre ACA); * Employer plans averages 6-10% increase per year * Individual plans averages 10-15% increase per year
Rollout (2010-2017) * Employer plans averaged 3-5% increase per year * Individual plans averages 0-10% the first couple of years, but spiked hard to 25%+ from 2016-2018.. with lots of volatility (one stat I found shows 130% increase between 2013-2019)
Post (2018 to today) * Employer Plans averages 4-6% increase per year * Individual plans were generally stable but with huge volatility; also expansion of gov't subsidies absorbed much of the increases for those earning up to 400% of fed poverty level
But when we talk about the ACA's impact on cost, we're always talking in a macro sense. Every program has individual winners and losers.
That's because NY had enacted a coverage mandate even before the ACA, so insurance companies were forced to offer policies to everyone. This resulted in a runaway spiral where only sick people were getting insurance.
The ACA forced all large employers to buy insurance, greatly increasing the risk pool.