What is he not good enough at yet? I think most posters say stuff like that because of his age, when he plays with far more maturity than some defenders who are 29/30. He can still improve like anyone but to say he's not good enough to be first choice for a couple of years is complete bollocks in my opinion.
Laporte isn’t slow but he isn’t the quickest, Garcia is slower than Laporte. Put Rodri in front of them and there’s zero pace in the defensive spine. Garcia is certainly mature beyond his years but he has made mistakes. To put it bluntly he is not yet athletic or strong enough to be a first choice for us in big games. He may never get quicker but he’s going to have to get stronger. You made comparisons with De Ligt- the difference at a similar age being that De Ligt was an absolute unit and bullied Lewandowski and others in the champions league - Garcia is nowhere near the same level yet.