Unless I'm missing something, it's only for 2 years after purchase?
"The legal guarantee covers any defects presumed to have existed at the time of delivery and which become apparent within a period of two years. However, the crucial period is the 6 months after you bought your product:"
That's the absolute EU mandated minimum. Per country it can be stricter. Also, generally businesses are expected to do somewhat better than "the bare minimum that makes you not want to demand your money back".
"The legal guarantee covers any defects presumed to have existed at the time of delivery and which become apparent within a period of two years. However, the crucial period is the 6 months after you bought your product:"
https://europa.eu/youreurope/citizens/consumers/shopping/gua...
So I'm assuming the bulk of older phones would no longer be covered?