I am wondering what is the relation between the real difficulty of the same rated problems now and 10 years ago. For example, if I solve 2000 rated problem from the previous round and from codeforces Beta Rounds, Which one will be difficult in general?
For problems with the same rating, recent rounds are more difficult.
It's hard to say, but from my experience, past Codeforces rounds have been more about "thinking"/observation rather than implementing. However, 10 years ago, there was much more implementation-based problems.
So it's hard to say because it's like comparing apples (implementation-base problems) to bananas (observation-based problems).