If he had played the way he did at his peak, Real Madrid would probably be picking him up again today. Like every football player, his problem is old age. As he gets older, he has to perform worse and underperform. That's why I don't think anyone would want him in Spain other than Sevilla. Anyway, congratulations to Sergio Ramos, who is preparing for a new tempo with his new team. I wish him success.
Madrid don't have a track record of buying and bringing back ageing players. Even if he does perform well enough in the end at Sevilla, we need to realise that Sergio is now 37 years old and he will probably only be at Sevilla for 1 or 2 seasons and then go on to retire / to an Arab club as the end of his professional career (most likely retirement).
Sergio is now one of the legends of Madrid and bringing him back at this age will only tarnish his fine form at Madrid and it would be better for him to stay at Sevilla as a defender while waiting for the end of his career.
At least he would still be very useful for Sevilla.