Real Madrid currently have some good defenders, at world-class level and they don't need to get defenders like Romero. Reason is that defender is no longer young enough for Real Madrid if they want to find youth defenders to prepare for future. They did it with midfielders like Camavinga, Tchouameni as preparations to replace Kroos, Modric, Casemiro and I believe they will do it with defensive players too. In front line, they applied same strategy with Vinicius Jr, Rodrygo and Endrick.
Real Madrid's front line and back line are actually quite good if we look at it for next season because Real Madrid's front line will also be complemented by Mbappe who has been brought in by Real Madrid itself. As for the back line, I think some of the players you mentioned are also quite complete for Real Madrid and if there are additions to the team's future plans, I think Real Madrid can still hunt for several more players through the transfer market every time the season ends.