Interesting - I felt this way about Project Euler, which within the first few problems was exactly as you described - heavy mathematical literacy. I haven't gotten far into an Advent of Code since 2015 (~18 days), but have done the first 5 days of 2020; no mathematical literacy needed.
For 2015, and 2020 so far - its mostly text parsing, data structure building and basic iteration/permutations.
Project Euler 1-50, maybe 1-100, is similar in difficulty level to Advent of Code, I'd say. After that it quickly starts to become about how much number theory you know.
That's true, the later problems are thought-provoking but have prerequisites. I enjoy number theory but I won't mess with currently. I plan to go back to them one day, not sure though :P
Project Euler is very specifically a website that requires both math knowledge and programming ability. It's designed to expose people to difficult math concepts, while advent of code is mostly explicitly for programmers.
I haven't found this years aoc to be too mathematical either. It seems more parsing related, i.e. extract all this info from a line of text is the hardest part.
For 2015, and 2020 so far - its mostly text parsing, data structure building and basic iteration/permutations.