Car insurance estimates can be accurate depending on how you get them. If you're just calling up one specific insurance company, you're not hearing all of your options. Similarly, online quote tools aren't really equipped to show you all your numerous options, either.
The best way to get accurate car insurance estimates is by working together with a local independent insurance agent. They can browse multiple car insurance companies for you and gather multiple quotes and estimates for the exact type of policy you need. Independent insurance agents aren't bound to any specific carrier, so they're free to get you several different, accurate estimates.