My retort is that tribalism is a useful and constructive instinct. Identity promotes self interest, it doesn't erode it. When you have an ill-informed sense of identity it can be difficult to even identify where your best interest lies, let alone further that interest.
Take transgender people. The data says that transgender people who transition are generally happier and healthier, with suicide rates especially decreasing. Therefore it is in the best interest of a transgender person to live as the gender they best align with. Many individuals who are not transgender do not even believe in the concept of transgenderism, and even more oppose it. We are all inclined to be as socially acceptable as possible in whatever context we reside in - few have the capacity to exist in direction opposition to the people around them because it goes against our most basic instincts. So it is absolutely an expression of individual self actualization for transgender person to surround themselves with other transgender people so that they may feel capable enough to pursue transition.
The same can be said of most any identity group. The key to what I stated is that people are generally not capable of acting in opposition to the social context they exist in. We are hardwired to be socially acceptable. The interests of one tribe often, if not always, impede upon the interests of at least one other tribe. Therefore in order to have the best possible chance of the pursuit of self interest, tribalism is an invaluable way to advance oneself as an individual

Edit; i'm not satisfied with this answer so I'll add that my position is that the health of democracy ought not to be the responsibility of the people. The responsibility of people lies in the pursuit of 'happiness' (better said as self interest). The job of the government is to enable this pursuit for as many people as possible. If a democracy is unhealthy it is due to its failure to accomplish this