A big difference between them, is that for Watergate, the country had high standards for the president. It was widely held that the president 'could not be a crook'. Not acceptable.
And so, what Watergate was about, was a battle between those who suspected Nixon, more and more, and those who 'trusted' his denials of crimes.
What happened over time, was that more and more evidence was uncovered, and Nixon denied more and more. As the evidence grew, Nixon took more drastic measures; he fired the investigator, and lost his top officials, trying to say 'ok, they made mistakes, but the president did not'.
He hung on as long as he could, and kept enough support to stay in office, until the tapes finally showed how he had been badly lying all along and most of his support ended - almost all the Congress, though about a quarter of the public still supported him.
A difference is that the trump supporting part of the country today Just. Does. Not. Give. A. Crap about his crimes. The standards are no longer the same. trump can do ten times the crimes of Nixon, and get a response from nearly half the country of 'good, that upsets Democrats'.
Democrats are following the same play of investigate, get evidence, prove crimes, and they're wasting their time with these people - and the Republicans in Congress follow the 90% Republican approval rating, not the facts.
So the situation has simply changed. Speaking of tapes, when the Hollywood Access tape came out, the initial reaction was, 'that ends trump's candidacy, he can't be elected' - and then he was elected.
So Democrats might be 'right' on the issue of trump's crimes, but the politics aren't the same. The country cared about the crimes and turned on the president they had recently re-elected by 49 states and left him with historic low approval under 30%.
Today, nearly half the country does not care. At all. And so, the whole situation, the politics, the rule of law, have changed. Guilt of crimes currently does not mean loss of support, forced resignation, accountability. Why that is is an issue for the country to deal with.