Someone else , who I think has since left the game, asked much the same question.
John has mentioned the usefulness of sets,and pointed out that you seem to have filled the top half , leaving little for the skills lower down, where the skills allocated in levels 11 ,and 111, have more effect, however, what he didn't mention specifically is, that there is no need to fill everything to maximum level available, just to the minimum required to open up the lower branches , especially if you are not using the unlocked skills, and the path ends in a dead end.
For example, in the second row below building and knowledge, the path left leads to lumber production, and is a dead end, and there is no need to do anything here if you have very little lumber production.
Two below that is ranged, another dead end if you don't use ranged troops,and two below that is scouts which doesnt need to be opened for onward progress.