Impeachment was partisan, and a waste of time. But you are missing why. The reason is because one side was doing its job, acting as oversight and a check on the Executive, while the Trump Party has made a choice to acquiesce to the popular (within their party) bully who leads them.
But whether it was a waste of time (due to the Trump Party's stonewalling) or not, it was necessary. The alternative - to just let him get away with it without even subjecting him to impeachment - would have been unacceptable. The Democrats can't just sit back and not investigate when the President refuses to release lawfully appropriated aid - Congress controls the purse, not the Executive. And they can't just sit back and do nothing when the President refuses to cooperate with a Congressional investigation - particularly an impeachment investigation. Investigating the Executive, and impeaching the president, are two more key Constitutional powers of Congress - not Trump.
Finally, they can't sit back and let the President marshal the might of US foreign policy and taxpayer dollars, to support his own political campaign against a leading Democratic candidate. If Trump wanted Biden investigated for legitimate reasons, he should have used legitimate means (like his own Justice Dept.). If he wanted to investigate Biden for political purposes, that's fine too - but it should have been done using Trump campaign funds, not US foreign aid and not US diplomacy. The Democrats would have been foolish to allow that to go on unanswered.
As far as I know, we still don't have a single document from the White House simply explaining why he held up the aid - who made the decision, and when. WH counsel literally couldn't even answer that question in the Senate trial. The Trump Party doesn't want to know. That's not just partisan. That's walking away from the checks and balances of the Constitution.
Now, what would change this picture a bit, is if the Trump Party decides to censure the President or continue to pursue documents related to how and why our money was withheld. So, consequences - but not removal from office. I can respect that. I suspect they prefer to do nothing.
May I remind you that at least two (that we know of) leading Republican candidates for President in the last election cycle, came out and said publicly, that Trump needed to be impeached for this behavior (though perhaps not convicted, they said - a position that I respect). John Kasich and Carly Fiorina. I strongly suspect more would have agreed, simply on the merits of the case, if Trump wasn't so popular within their voting base.
By the way, Trump is charged with violating several laws under the umbrella of the articles of impeachment: obstruction of Congress, the Logan Act, the impoundment act, the whisleblower laws and FEC laws forbidding soliciting or receiving anything of value from a foreign government in connection with a political campaign. Trump has repeatedly flaunted such laws, this wasn't a one-off mistake .. he's going to keep doing this stuff. Impeachment may make him think twice next time, even if he was acquitted - or it may not - but doing nothing is not the right answer.
The right answer would have been for the Trump Party to man up, and stand up for what is right.