eIDAS is a cartel created to protect the business interests of EU biggest certification authorities.
It is a digital certificate standard. Browser certificates is only a tiny part of it, that wasn't why it was made. Having a standard for digital certificates is a good thing, it makes it easy to switch document signer provider etc since they all are forced to implement the same interface.
eIDAS was introduced in 2016. Now 7 years later there still isn't a API specification for interoperability (there are drawings though https://blog.eid.as/new-apis-for-the-eidas-ecosystem/ )
In the meantime, any digital signature done in EU must be done with a certificate issued only by the "select" CA to be considered "valid".