Furthermore, speaking of Real Madrid, you're right. Real Madrid can't continue to rely on their aging defenders. Their performance is certain to decline and they are also prone to injury. Therefore, Real Madrid must bring in new defenders to strengthen their defense and improve. However, after I investigated, Real Madrid has actually brought in three new defenders: Dean Huijsen, Alvaro Carreras, and Alexander Arnold. All three players are quite formidable defenders. So Real Madrid should be able to strengthen their defense even more with these three new players.
Huijsen is a promising central defender while I don't know of Carreras and Trent does not have good defensive skills. Real Madrid surely knew defensive weakness of Trent and they perhaps plan to use Trent mainly for attacking support. Real Madrid will not accept to lose La Liga title to Barcelona again and they are improving their squad with new players.
Barcelona have a young team that can grow up more but their brightest star player Lamine Yamal shown some signals of being distracted by parties and unhealthy living styles. This can harm Barcelona attacking power in next seasons and give Real Madrid kind of good opportunity to not only challenge Barcelona but also take trophy back.
Real Madrid is a very good team, and their transfers were truly excellent. Barcelona, on the other hand, built a superb squad with fantastic players from their youth academy. They finished last year as champions and dominated Real Madrid in every match they played. Unluckily, they'll be considered for the Champions League semi-finals; had they reached the final, they might even have had a chance to win the trophy. From this perspective, the rivalry between the two teams is fierce. Real Madrid is in much better defensive form this year and will have a much better matchup against Barcelona. They likely won't lose to Barcelona in every match they play against each other this season like they did last year. They've made some significant signings this year to forget last year. We'll have to wait and see how the season plays out.