I assume then that Humana Medicare HMO is a Medicare Advantage plan.
Those with Traditional/Original Medicare (Parts A, B and D) and a good Medigap plan can self-refer to any doctor who takes Medicare. You can change plans for 2024 next October. Unfortunately, people who don't start out with original Medicare may find their Medigap policy to be more expensive than if they had started out with it in the beginning, and the insurance company can refuse to take you if I understand correctly. But you would then be able to see any specialist you want without needing any referral.