Weird, the Orthodox you've spoken to may be referring to the idea that she is still subject to the fallen nature of humanity (though not any personal sin), or they may be poorly catechized. Or their churches have been lying to me 😅

Re: Ephesus you said she was "named" and I thought you meant the Council gave her a title, rather than affirming something that had been in use before. No prob.

Obviously there are heretical sects like the Palmarians or various South American "Catholic" groups that take Mary veneration too far. But the apostolic churches all uniformly orient their worship exclusively toward God, and Mary is not the focus of the liturgy/Mass.

When you say "overemphasize" do you mean that there's a fundamental problem with how the church views/allows a veneration of Mary, which leads to some people focusing more on her than God? Or that individuals are performing an acceptable practice and taking it too far? You say things like "overemphasize" but it also sounds like your objections may be more categorical than quantitative, and I don't want to strawman you.