Maimonides and Kabbalah

After all, both are sacred and have been accepted in tradition as correct and true, so how can two truths contradict each other?

There are disagreements in law and thought. This concerns the general question of how to address disagreements (these and those are the words of the living God, etc.). In my opinion, one is right and the other is wrong, but both are legitimate. Everyone will choose what seems more reasonable to them. Sometimes there is no disagreement, but rather a description in different language of the same matter or of different angles on the same matter.

Just out of interest, I assume you chose the Rambamist side in the context of this controversy?

I don't usually choose sides (i.e., the method of one sage in a sweeping manner). Each issue is unique. In general, I don't deny the existence of spiritual worlds and spheres (whether as a metaphor or in reality). But certain explanations of Kabbalah seem dubious to me. I don't think all of this came down from Sinai, and there are many additions that are based on the understanding of various sages and about which one can certainly disagree.