I agree that you should be able to get in contact with the website owner. However, I believe it'd be better if a person had to at least query denic to get your address. That's easy enough if you have to resolve a serious matter and the website owner is also a bit more protected against abuse of their data.
An email address is no Vorladungsfähige Adresse. You can't sue that, you can't send a Gerichtsvollzieher to it, and you can't seize the owners assets with it.
If I want to send an Abmahnung to a website owner, because they publicly defame me — as has happened before — then I need something stronger than an email address. Or I need to invoke the right to be forgotten, but I don't want to do so, I prefer having a way to eliminate the source.
The law just requires a way to contact a person within of a few days, and a way to be able to get the person behind a site to be able to sue them.
The alternative is sites that you can't do anything against if they act illegally against you, e.g. through libel and slander.