Then you're risking political backlash jeopardizing the 2020 election.
I've come to believe that kind of thinking communicates a lack of sincerity in our principles. We either communicate that we hold the rule of law sacrosanct or we communicate that we want to win elections.
While we can draw important lessons from 1974, 1999, 2016 and 2018, it would be erroneous to force today's circumstances to be a mirror image of any of those years. To whit...
1974: The charges that led to Nixon's impeachment would be at least the same set of charges that would lead to Trump's impeachment. Problem: Nixon was not the head of a populist movement and was therefore vulnerable to changing sentiments within his own party. (Note that this does
not help my argument, and I'm not claiming that it does).
1999: Impeachment of Clinton led to rising approval of Clinton and crashing approval of Republican. Problem: Republicans won control of the Executive and Legislative branch in 2000 anyway.
2016: Clinton emphasizes criticism of Trump (or, at least, the media prioritizes her criticism of Trump), causing any of her policy positions to appear to be ancillary. Problem: Yes, she lost the election, but there is a metric butt-ton of reasons why she lost, and it's difficult to single this out as a driving factor for her loss. There are other more measurable reasons for her loss than this.
2018: Democrats overwhelmingly take back the House based on candidates pushing policy over anti-Trumpism, in particular due to their emphasis on health care messaging. Problem: at that point in time, Democratic candidates could afford to let Mueller handle the investigation, giving them the space they needed to focus on policy. Only now, the Mueller investigation has ended, and he concluded with a report that quite specifically handed off responsibility to Congress to address. To ignore this responsibility is to pretend that Mueller has not placed the ball squarely in their court.
There's a final problem you're not factoring in, which I laid out in post 23 (a post that you hit "like" for):
If Democrats don't move forward with impeachment, they'll create a vacuum that Trump will fill. And what he will fill it with are massive investigations into the FBI, Democrats, Clinton, Obama...you name it...all with AG Barr as his general. Barr will roll right over the traditional barrier between the DOJ and the SDNY as surely as Trump steamrolled over the traditional barrier between the White House and the DOJ, and one after another, every Federal investigation into Trump and his businesses will be terminated. And by 2020, you'll see one or more Democratic Presidential candidates under investigation by the DOJ.
Democrats may think they have the luxury of waiting, but Trump has no intention of waiting for anything. Trump is in full authoritarian mode now, and if he senses weakness and hesitation in the Democratic party, that's it.