So, because the GOP is now no longer a force for good, or even one which can be relied upon to mitigate evil, there is no longer any choice than for it to be greatly damaged for the good of the nation. Please keep in mind that I say this as someone who, before 2016, honestly thought that Republican control of Congress was vital to the future of our nation and my two small children.
If Republicans maintain their majorities in both houses of Congress–which I believe to still be very possible–Trump not only will not be impeached (there is already very little chance he will ever actually be removed), but we will likely never even know the full truth of what really happened in the 2016 election, or about the many scandals which the Trump administration has perpetrated. Meanwhile, the Republican Party will believe, not without good reason, that embracing Trumpism has no electoral downside and that this philosophy, far more consistent with third-world dictatorships than with the United States of America, should be the way of the future.
Seeing Nancy Pelosi and Chuck Schumer in power again would literally pain me (the existence of both of them, especially Pelosi, is actually greatly harming the Democrats’ chances of regaining their majorities). However, that price would likely be smaller than the long-term risk of allowing Trump and his movement to fundamentally and forever alter not just the GOP, but our international alliances and the nature of our politics/culture.