You have a mistake in your assessment of Earley parsers. For ambiguous grammars and input, they do not return an arbitrary tree, but all possible trees. In this regard they are no worse than yacc: "the user resolve[s] these manually" by picking the correct result(s). To a human, it's visible at a glance which is the correct result(s), entirely without needing to learn how to decipher these bizarre warning messages you mentioned.
> conflicts are a strong sign of a bad specification of the language
So what? That's not pragmatic thinking. We cannot go back in time and influence the design of ambiguous computer languages so they are not ambiguous. Natural languages never are without ambiguities!
The parsing job needs to be done, no matter the complexity of the language. Instead of wishing it weren't so, just use a tool that can deal with it. Earley parsers can, yacc cannot.