Cluster Rush could use a power down for the following reasons:

While it is possible to overcome it using baseset, doing so requires extensive practice and memorization of the line, which even the best players struggle with. I don't like it when getting a draw is the best you can get without studying all the lines, even though getting there is a little bit easier.

Because it is so simple to implement, even average players may use it to their advantage and dominate the competition.

Even though random set units are intended to be weaker than baseset, I've seen that in roughly 40% of B+8 sets with cluster rush, there isn't a single random set unit that can beat this rush.

Even though the rush might be an autowin with the Venge cannon, Gauss Charge, or Nivo Charge, it at least forces a draw or mirror. (I haven't tested this much, so I don't know for sure.)