@brrrrrrrrrrrrrrrrrrrrrrrrrrrrr
Patriotism’s sole purpose is to persuade people to do unreasonable and unjustifiable acts which bring harm on the individual for the benefit of the state.
Like pay taxes, volunteer, and vaccinate? (Leaving aside, risk their lives to try to defeat fascism).
Even with the individualistic lens you apply here: a failing state doesn't serve individuals well either, so ties that bind and inspire at that level are useful.
And finally, there are many individuals for whom a national identity gives value and meaning and belonging, transcending race or religious or social differences.
The people I've heard the most sincere and vocal patriotism from have pretty much all been immigrants, mostly from countries where to be outside the favoured elite, or outside the majority group, is much worse than in the UK.