Why didn’t the polls getting it right in 2018 change your mind?
Because Trump wasn't running in 2018, so the situation is not analogous. I too am still distrustful of the polls, but am somewhat hopeful because turnout has been high and Biden's lead relatively steady. My bigger concern though is the shenanigans Trump will undoubtedly pull to try to interfere with the vote and subsequent counting of it.
Here in Minnesota, we were told that mail in ballots could be received until 7 days after Nov 3 as long as they were postmarked by that date. That has been reversed (surprise) by a Federal court now, and ballots have to be
received by election day. Either way is OK, but changing the rules at the last minute could result in a lot of ballots not being received in time.
I partially blame the election commissioner of MN though, because he extended the deadline past what was set by law, thus it was overturned by the court. If he had just left things alone, there would have been no confusion. He said
all ballots will be counted, and late votes will have to be challenged, which they obviously will be if Trump loses. So even in Minnesota, known for its efforts to get good voter turnout, there is a strong potential for a serious cluster f**k determining the final vote.
Edit: Dems in particular are now urging those who have not sent in their ballot to drop them off or vote in person. I can just hear Trump now, "Those Dems are voting twice, I told you so. The election is rigged." Obviously mail in ballots should not be counted if the person voted at the polls, but even a few mistakes allowing a double count will give Trump a lot of ammunition. At least my and my wife's ballots have been received and will be counted.