Ramos began his career in Seville, and I assume that he will finish it there. After his decision to move to PSG, it seems to me that with this decision he made his return to Real Madrid almost impossible. Yes, he is a very good player, but to end his career as a Real Madrid legend, he needed to remain in the team. With PSG he was unable to achieve anything significant, moreover, he was often plagued by injuries. Now he has returned to Seville and this is quite symbolic, he is playing where he started.
PSG couldn't manage the behavior and inconsistent form of Sergio Ramos. With the constant unavailability for matches and this is really one big miss for them. Sergio Ramos is aggressive defender and have won the major titles with Real Madrid before leaving for Sevilla. He's an experience defender and a keyone for every manager and club he played for.