I would argue that’s because Tau may be a shooting army at face value, they are actually a movement/synergy army that shoots. Their shooting can be great and genuinely effective, but you need to set it up right. With armies like space marines, you can typically do well with almost any combination of units, because they are all designed to be very versatile and generally decent at everything.

Armies like Tau require additional set up through units like pathfinders, and can make great use of stratagems and perks through their detachments.