Depends on who you ask. Membership in and of itself is not required for anything except membership. However, there can sometimes be strings attached such as refinancing options for student loans, discounted malpractice/life/disability insurance, etc where you are required to maintain your membership for the life of your loan/insurance policy. As long as you make sure you don’t have anything tying you to membership, you can feel free to renew or not renew as you please. There are pros and cons to each side.
I will admit I am not a California CDA member (I’m part of the other CDA in Colorado... for now), but this is usually how “organized dentistry” works. Just be aware that some states won’t let you be a part of the ADA alone and make you also join your state association— so if you don’t renew one, you may not be able to renew any.