I concur with Biden. The Mueller investigation is ongoing and, so far, Trump hasn’t done anything outside of American Presidential tradition that’d warrant impeachment. Democrats need to focus on real issues, not whether or not Trump said something mean on Twitter and if that makes him deserving of impeachment or not.
He is in clear violation of the Emoluments Clause. He was impeachable the moment he took the oath of office. While unquestionably the de facto holder of the office, his entire term is illegitimate.