Can you please elaborate on what you mean by decentralized/centralized wallet? As mentioned above by decodx, I feel you mean non-custodial /custodial.
If the wallet gives you access to your private keys, it's a non-custodial wallet. Otherwise, it's custodial. Is this what you meant?
However, all wallet software is centralized (whether open source or proprietary).
Is bitcoin core centralized?
You don't rely on any third party when using bitcoin core and I don't think it's true to say that bitcoin core is a centralized wallet.