It's never good when someone denies the legitimacy of the very system that brought them into power. This is the part that makes him "terrible for democracy".
Embezzling every penny he could, modeling himself after Hitler, raising a mob to storming the capital to kidnap the vice president, and filing fake lawsuits about the election, was far far worse than losing the unofficial popular vote.
50 million+ people voted for a republican or non-democrat, they didn't vote "for trump". Just like when Biden won, 70 million+ people weren't voting for Biden, they were voting for a democrat, non-republican, or more specifically: anyone but Trump.
It's insanity when there are, for all intents and purposes, two people on a ballot to say "we chose this person specifically!!!". No you didn't, you chose one of the two options that was given to you, and since they are normally on the opposite end of the political spectrum you just chose the one "closest" to your views out of the two. Almost everything that happened up until that point is literally out of any normal individual person's control.