YOu can break quarantine if you're on the essential list of workers to go to work only. So if you need food, you have to have someone drop it off to you. Like our to and from gun laws.
If you're not listed as essential, then you have to quarantine.
If there are exceptions to a rule, then the rule might not be as effective as the rule makers pretend.
If 20% of the population are essential, and visits to those essential businesses and services by nonessential people are allowed, then that's a huge percentage of the population.
We didn't see a huge increase in infection rates among nonessentials going to get food, medicine and guns, nor among the essential employees -- Maui Hospital being an outlier. That includes the time before masks were mandated.
Therefore, the lockdown was not needed. However, having said that, from a human behavior perspective, more people failing to social distance could have created a spike in cases, because we all know many people can't break their handshake/hug habits when greeting people here. If social distancing and hand washing combined to become the magic bullet that kept case numbers low, and self isolation kept people from screwing that up, then it can be argued that the lockdown helped.
Bottom line: We could not predict the effectiveness or ineffectiveness of a lockdown before it was tried, just like we can't now play "what if" using one or two facts from the last 4 months. The situation is much more complicated than "lockdown vs. no lockdown".
It's like asking, "Why do you wear that garlic?" Answer: "To keep away Vampires." "Does it work?" "Well, I've never been bitten by one!"
The people who think the lockdown is what kept us from getting a large number of infection cases will say the lockdown was the reason.
The people who think the lockdown was ineffective will say it was everything else we were doing that worked -- with or without a lockdown.
You can compare locations, like Georgia, where they ended the lockdown earlier than most as an example proving the lockdown helped nothing. Since they were locked down for 2 months before lifting the order, you'll never be able to use that as proof, though. What it proves is that the lifting of the lockdown didn't create a second wave of infections -- nothing more. Different weather plays into that analysis, too. Warm, humid conditions have been linked to reducing COVID-19 infections.
In the end, nobody can change the past. Nobody can predict the future. The next pandemic might require isolation to prevent a full-on plague, but we'll be using this pandemic as evidence that lockdowns are not the answer.
We don't know what we don't know. Once we figure it out, it's often long after that knowledge could have been useful.