...dominiert teamorientierte Projektarbeit über unwichtiger werdende
Hierarchien.
By separating the words and using the comparative it seems better to me. "Unwichtig" is a normal adjective here, not a prefix to "werden". And "become unimportant" is rather "become less and less important" here.
But there is a kind of mismatch in the comparison:
The singular/plural does not match. "teamorientiert" is defining, while "unwichtig werdende" is declaring (and questionable). It is logically not clear what the cause and effect is.
I would formulate:
Wegen des Aufstiegs der Wissensarbeit dominieren teamorientierte
Projekte mehr und mehr über hierarchische Ansätze.
Now, "Ansatz" is nothing interesting, but just like Wissensarbeit it should be possible to find something from the context. "Hierarchien" alone is not enough, no matter which language.
I also eliminated the doubling of -arbeit in Wissensarbeit and Projektarbeit.
The "mehr und mehr" picks up the movement of "Aufstieg" and in the end replaces the original "unwichtigwerdende".