Real Madrid invests money but they always invest money in the right places and not spend huge amounts of money in the wrong places like other teams. All the signings Real Madrid have made since then have been successful. Many criticize the signing of new players when Real Madrid sign them but every time Real Madrid have proved them right and the critics wrong.
Although not 100% of their transfers were successful, most of the transfers were successful. Barring a few transfers, they have been successful in finding players in most cases because they have made the right decisions. The two players you mentioned may not have performed as well as they thought they would or they didn't perform the way they signed for so much money but if you look at the other deals you shouldn't have any doubts about their transfer.
Ronaldo, Cristiano Ronaldo, Sergio Ramos, Luka Modrić, Karim Benzema, Rodrygo, Vini Jr. these transfers prove that Real Madrid is better than other teams in the transfer market.