With the exception of those who are colorblind and have a legitimate problem spotting the trees, they are honestly NOT that difficult to find. Most of the reason people are not finding trees has more to do with needing to refresh (leave the town and return) than with them actually being hard to find.
On the point of 'detracting from the main game'...since the buildings you can win can have a significant impact on the 'main game', I would argue that the 'detracting' is more than fairly compensated by the reward gained.
As far as quick and easy goes...well, you are right, it was 'easier' to just click the soccer event than it is to find a tree. On the other hand since every tree you find is guaranteed currency - which was not true for the soccer event unless you chose the lowest level (and least efficient) reward - I again would argue that the extra effort is well rewarded.
To the devs, I say: Good job on a great new event