This happens with every update because the game engine has changed due to bug fixing etc. and replays, which are just lists of commands for the game engine are not compatible anymore. Hopefully there will be a compatibility mode to watch old replays in the future.
Sometimes the internal format of a file changes when a program changes. That is fairly easy to compensate for by including the format version number at the beginning of the file. The newer version of the application would be programmed to also understand the older format.
With AOE2, I believe there is a more significant challenge than simply the format of the file. The replay files favor being compact as opposed to verbose. So, the data in the file describes the minimum information (villager has been queued, unit has been tasked to go a certain direction). Then, the file relies on the current game rules to determine the actual behavior of the units (how many resources a villager is generating, how much damage a military unit is receiving from an attacker). When the game rules change, such as when wheelbarrow takes effect or how much stone is being mined, then the replay no longer matches the game as it was originally played, because the rules changed.
To fix this problem, the developers would need to develop a new type of save file that is larger but completely expressive stand-alone. This would have the added benefit of allowing more detailed statistics. But, it would be a lot of work.
thank you very much. I understand, the patch now was apparently to fix resource gathering when it takes effect. I hope they find a solution, maybe by playing the file with the old version of the program files or something like that. It is quite a thing for the community and a solution would definitely get a lot of hands clapping