2020 was obviously a very unique election because of the mail-in voting. There are various data on that (and this is not partisan whatsoever) available here [1]. You had 40 million more absentee/mail-in ballots than in 2016, paired with what were many extremely bizarre statistical changes. To give just one example, in 2016 the percent of rejected ballots that were because a person had already voted in person was 1.3%, in 2018 it was 1.4%, in 2020 it was 13.5%!
I didn't vote for Trump and don't really have a horse in this race, but I also don't feel comfortable with mail in voting as a meaningful percent of all-votes. This is even more true as the entire country becomes more polarized and radicalized. This sort of mentality is going to motivate an increased number of people to try to cheat the system, and encourage "selective vigilance" from those involved in guaranteeing the integrity of the electoral process.
And perhaps the most important point is that in terms of how a democracy functions, whether elections are fair or not is a secondary concern to whether people think they are or not. The main benefit of a democracy for a society is stability. People looking to change their political future were able to set aside their pitchforks and pick up ballots. But when people don't think those ballots matter (even if they do), then we're back to square one.
[1] - https://ballotpedia.org/Election_results,_2020:_Analysis_of_...