The record for presidents is mixed. I believe the sitting president SHOULD visit all 3 sites on each anniversary.

But they have done it in different ways:
- Biden and other former presidents were there in 2021: https://www.nbcnews.com/news/us-news/9-11-anniversary-moments-silence-be-held-full-day-memorial-n1278972

- Trump was in Shanksville PA in 2020: https://www.nbcnews.com/news/us-news/9-11-anniversary-moments-silence-be-held-full-day-memorial-n1278972

- And others have done it from the WH: https://apnews.com/article/sept-11-terror-attack-anniversary-ceremonies-47488758b18fd78f541674041e36d263#:~:text=Biden%2C%20a%20Democrat%2C%20will%20be,White%20House%20lawn%20at%20times

So no, Biden is not the "First president not to visit world trade center"