>>96410864
Tau are fundamentally the worst faction in 40K with perhaps the exception of the Fireside Enclaves. They're naive to the point that they unironically didn't realize that the walking battle cathedrals were real (whilst having mecha gundams themselves). They're aware of the warp but had no idea that there were predators in it waiting to consume sentient souls. Worst of all they got the ego of the older races without actually having any real accomplishments.

Even the Eldar theoretically outnumber them, think about that for a second. They're outnumbered by the dying race of space elves and are trying to pick fights with the Imperium. If they weren't carried by the fact they're an established faction they would have been wiped out by a penitent crusade by now.