Richard Nixon was named an Unindicted Co-Conspirator in the indictments of Haldeman and Ehrlichman, and even this did not create a majority for impeachment. If that was as far as it got, Nixon would have been unpopular, but he would not have been removed.
There's no smoking gun in Mueller's report. There's no statement stating Trump obstructed justice, and no naming Trump as an Unindicted Co-Conspirator. Trump has certainly not avoided the appearance of impropriety, but to say that the report justifies impeachment is wishful thinking.
The “smoking gun” tape in Watergate was just a recording of Nixon and his chief of staff discussing a plan to ask the CIA to ask the FBI to shut down its investigation. How is that different than Trump repeatedly ordering his officials to find a way to shut down the investigation?