Does anyone actually know how university rankings work or do we all just pretend?

I've been seeing so many posts about Warwick's ranking going up and down and everyone acting like they understand what it means. One day people are celebrating it overtaking Oxbridge, the next week someone's posting about how it's plummeting. I've looked at the methodology for these things and it seems to change every year based on arbitrary factors like international student satisfaction or how many papers got cited in one specific journal.

Do employers or academics actually care about year to year fluctuations or is this just something we obsess over because we want validation that our uni choice was the right one, I'm in my final year and I still don't know if any of this actually matters once you graduate. Does anyone have a genuine insight into how these rankings are used, or is it all just a game to make us anxious about things we can't control?