This relies on the voter to have enough autonomy to be able to independently access their online ID. It would be easy to circumvent by separating the voter from their ability to identify themselves online. Either by keeping their means of identication from them during the voting period or by being the gatekeeper to the computer where their online ID is stored, for example with a password.
It also relies on the voter caring enough about their vote in the first place to be willing to attempt to do it, with whatever possible personal risk that entails.
The id is a physical card, where the private key and the data attached to it can be accessed through NFC. Sensitive data can be accessed through specific applications, public data can be accessed through a simple NFC reader.
And yes, if the government is corrupt in its entirety, from creating IDs to the ballot process itself and to sequestering citizens, then yes, you're fucked. But I don't see how that would be different for paper ballots or any other means of voting.
It also relies on the voter caring enough about their vote in the first place to be willing to attempt to do it, with whatever possible personal risk that entails.