It's not a problem really. We could sign like 10 promising middlefielders(not literally),loan them for a few years ,some are bound to be sold for a profit or turn into really good players to keep. Like others here already said,it's something similar to what Chelsea is doing. Jese,Isco,Morata & Illara were 4 of the most talented young Spanish players a few years back and we got both Isco and Morata. There is a difference since we already had Jese and Morata but you get my point. Out of those 4 promising Spanish players 3 really payed off. Isco will play for us,so will Jese. We sold Morata for huge money and we can buy him back too. We could also sell Isco and Jese for huge profits but it's better to keep them. Ceballos,Vallejo,Asensio and Borja Majoral are like 4 of the most promising young Spanish players (just like Isco,Illara,Morata and Jese were,what a coincidence. This time 1 was in our Castilla unlike previous 2) atm so we're doing the same. Vallejo is dubbed the new Ramos/Pique(mostly Ramos), Ceballos is called the new Xavi, Borja(Raul/Morientes) and Asensio(idk what they call him). It's a circle that will always happen. Talented young players will emerge and all smart big clubs should do their best to sign them.
Vallejo - 5 M fee
Ceballos- (if it happens) 12 M (maximum)
Asensio - 3.5 M
So we got 3 of the most promising young Spanish players for 20 M,which is freaking peanuts. Transfer ban of Barcelona helped for sure but it's still a huge mistake from your board to let this situation happen again.