I have no issues with contesting an election and never stated that I did. In my opinion Trump had every right to contest those results. He had an obligation to his supporters to do so. Let's discuss some of the differences between 2020 and the elections you brought up.
First difference. there's a difference between contesting the results of an election and questioning the legitimacy of an election.
I did mention that Trump lost in all but one of the over 60 cases he and his lawyers took to the courts. If you doubt this or think it's from a vivid imagination you can find many sources from independent reliable news agencies that back this up. Unlike 2000 where the recount was ordered to be stopped in order to comply with the time frame set forth by Congress to certify the results, Trump chose to go in a different direction and encouraged his followers to not only follow along, but to actively participate in disrupting the certification process. Violence wasn't a concern - "It's going to be wild!" Like everything else I'm mentioning in this post, it can all be verified by valid, respected, independent news agencies both domestic (US) and foreign.
In 2000 it came down to the infamous "hanging chads" and both sides had their teams of lawyers in Florida. The Dems got out played by Roger Stone and his Brooks Brothers Riot. The Dems bought knives to a gun fight and lost - which wasn't a surprise at all. Bush fought harder, Gore didn't, Bush won. It wound up going to the Supreme Court. On December 13, 2000, just a little over a month after the election and before the Electoral College votes were to be certified, Al Gore formally conceded his loss saying,
"for the sake of our unity as a people and the strength of our democracy, I offer my concession." To this date Trump has neither formally or informally conceded his defeat, and certainly didn't act in any way for the sake of unity as a people and for the strength of democracy. On January 6, 2000 twenty members of the House of Representatives rose one by one to file objections to the electoral votes of Florida. Gore, who presided in his capacity as President of the Senate, ruled each of these objections out of order and the electoral votes of all 50 states were certified. Bush was sworn in on Inauguration Day, and Gore was there to witness it. Quite different than 2020.
en.wikipedia.org
In 2004 Kerry conceded his defeat to Bush on the day after the election. There were concerns about the process raised by both sides, but I don't see the point of bringing them up since they were raised by both sides, Kerry conceded, and obviously there were no issues as far as certifying the results of the Electoral College. Bush was again inaugurated and Kerry was there to witness it. Again, quite different than what happened in 2020. Here's a link on the controversies if you're skeptical that these aren't facts and instead the product of a vivid imagination or just interested:
en.wikipedia.org
2016. The Associated Press called Pennsylvania for Trump at 1:35AM EST, putting Trump at 267 electoral votes. By 2:01AM EST, they called both Maine and Nebraska's second congressional districts for Trump, putting him at 269 electoral votes, making it impossible for Clinton to reach 270. One minute after this, John Podesta told Hillary Clinton's victory party in New York the election was too close to call. At 2:29AM, the Associated Press called Wisconsin, and the election, for Trump, giving him 279 electoral votes. By 2:37AM, Clinton had called Trump to concede the election. On Wednesday morning at 2:30 a.m. Eastern Time (ET), it was reported that Trump had secured Wisconsin's 10 electoral votes, giving him a majority of the 538 electors in the Electoral College, enough to make him the president-elect of the United States, and Trump gave his victory speech at 2:50 a.m. Later that day, Clinton asked her supporters to accept the result and hoped that Trump would be "a successful president for all Americans."
There were controversies and concerns; like in 2004 coming from both sides. Jill Stein contested electoral votes in certain states, but she's Green, not Democrat, and as I mentioned, there's nothing wrong with contesting, but when you lose, you lose, and if you respect the democratic process you put on your big boy pants, admit defeat, and for the good of the country wish the winner success during their term. As in '00 and '04 elections you brought up, the '16 results were certified on the required dates. People took to the street in peaceful protest (as is their right as Americas) which were not called for by the loser Clinton. No actions were taken by Clinton to mobilize her supporters to deny the results, take over the Capitol Building, "fight like hell," and disrupt the certification process. The protests did not involve police officers being beaten by protestors and protestors did not search out elected officials inside (or outside of) the Capitol Building looking to hang them or otherwise bring violence.
There's nothing wrong with contesting results and using lawyers and the courts to fight as hard as you can for as long as you can right up until the moment where Congress fulfills their Constitutional duty to certify the results. But 2020 was the only year where that long tradition of respecting the democratic process and peaceful transition of power was not only ignored, but pissed on.
For the record, the last time I voted Democrat in a Presidential Election was Clinton in '92; more because I was tired of 12 years of Reagan/Bush than I was a fan of Clinton. I was so disappointed in the Clinton years that I didn't bother voting in '96 which was made easier since I was outside of the country in a remote location and didn't feel I had anyone to vote for anyway. In 2000 I voted Nader. Out of the country in '04 and '16 (were I also wasn't a fan of Hilary and didn't vote for her). I'm not a fan of Biden either. Obviously I'm not a registered Democrat. What I am is someone who respects the democratic process and who is against authoritarianism. I'm also someone who accepts the reality of a situation without feeling the need to make up stories or deny reality when things don't turn out the way I'd like them to. I remember what I was taught as a child playing sports and am either a gracious winner or accept graciously accept my defeat without whining about my loss. And since my residence is not even close to being a swing state I've never felt bad about not voting because unlike declaring a winner based on the popular vote, the Electoral College system makes it so that your vote doesn't really matter if you live in a solid red//blue state like Alabama, California, W. Virginia, Oregon, etc
As far as Milei, of course his opponents are going to smear him and work to ensure his defeat in the next election. It's called politics and it's how that game is played and has been played since politics has been around. Surely you don't get upset when Trump smears people and works to defeat them in the next election since part of Trump's whole schtick is to give people childish nicknames and smear them before the self-proclaimed Billionaire tries to sell common people red hats or flat out begs them to send him $. And his supporters love it when he does and repeatedly open their wallets to give their hard earned $ to the most successful businessman history has ever known - so successful he has to sell hats, bottled water, steaks, etc., and beg for $ . I can't understand why you'd be upset, take offence, or even bring it up as an issue if other politicians and their supporters use the same smear tactics that Trump uses? Maybe that lack of understanding explains why you believe the 2020 election was no different than 00/04/16? The Devil's in the details.