The key problem with exit polls (in non-pandemic years) is that they are non-representative until the whole vote is collected and they can be re-weighed.

"exit polls are eventually weighted to match the final results, but that only happens after the election is over. On election night itself, the numbers are reweighted as more data becomes available, but what you’re seeing is still subject to a lot of uncertainty"

https://fivethirtyeight.com/features/exit-polls-can-be-misle... has a good discussion.