Does every problem need to be solvable by everyone?
Project Euler used to say something along the lines of "not everyone can solve every problem, and that's OK". Looks like they've removed that statement though. I remember encountering it early in my career and realizing some problems I cannot solve, even though others can.
Project Euler was one of the first programming puzzle sites. I give credit to them for my interest in programming puzzles. However, I quickly abandoned them once I found other sites that was less math focused.
For my personal goals, I want to get better at programming and not at math. When I find myself spending more time on the math rather than programming, I just skip the problem. I suspect many people abandon Project Euler for the same reasons I encountered.
With all that said, I agree that not everyone can solve every problem and that is ok.
It's pretty daunting when you're invested into something, spent a plenty hours only to realize that you're not in those 5% who's going to complete this challenge.
IMO AoC should strife to be completable by 80% of programmers (number is out of thin air, but you got the idea).
I for one want that 5% to have interesting challenges, even if I can't be a part of that 5%. Unique achievements should be meaningful and celebrated, not removed for fear of upsetting the majority who cannot achieve them.
While I agree with the sentiment of creating accessible content I think if you make the problems so easy 80% can solve them, what fraction will have fun doing so? Wouldn't say 50% find them trivial and boring/unsatisfying?
I think AoC goes for slowly growing difficulty which helps keep more skilled people engaged.
For what it's worth, I'm not a (professionnal) programmer, and I can usually solve 80% of the AoC problems intuitively. That's OK for me.
For the other 20% where I don't even know where to start, I look up a solution on reddit, try to understand it and re-implement it myself, and learn something new. The 2020 day 13 problem mentioned by GP was indeed one of those for me last year.
Honestly, I didn't even understand how the CRT applied even after knowing it was required. This visualization[1] is what eventually helped me solve it.
What's the main difference (besides submitting an answer faster than anyone else) between Project Euler and AoC? I find both rather similar (and I can do Project Euler any time of the year)
Project Euler problems seem to be all math based, at least as far as I've seen. Advent of Code problems have numbers as results (most of the time), but aren't always based on some mathematical formulation(s).
See 2019's IntCode puzzles for instance for something very far from Project Euler. They also had the side-effect of benefiting anyone who spent time refactoring their initial versions to create a better interface, a later day (23?) has you run 50 IntCode computers concurrently and communicating with each other. This became very hard to actually implement for many people because of the structure of their simulator and how they'd handled concurrent simulations earlier.
Project Euler used to say something along the lines of "not everyone can solve every problem, and that's OK". Looks like they've removed that statement though. I remember encountering it early in my career and realizing some problems I cannot solve, even though others can.