Alcaraz is without doubt the most talented of all young players at the moment. However, that doesn't mean other players can't get closer to him. There are several ways to become number 1 in the world. Roger Federer and Murray are good examples of this. Federere is a player who was incredibly talented, perhaps the most talented ever. But Murry managed to beat him a few times because he worked harder for it, trained harder but also put in more effort to win points. You can go far with a fighting spirit. And Djokovic has both, which is why he has won so much.
It is normal that even the best players in the world can not win all matches. Nadal is the best ever on Clay and his record on Roland Garrod will probably never been broken but also he lost (2 times I think). That doesn’t mean he did put less effort in but sometimes you have a less good day and your opponent has the best day of its life.
Every great game must have experienced defeat in a match, whether due to injury or other obstacles, there will definitely be a day when he can get defeat.
Nadal is probably the best player on Clay and his record is hard for other players to break but it's true as you said he has even had defeats so no player really has a winning record without a single defeat.
Even if there is, it is only temporary and in the future you will definitely experience defeat because more and more players get older every day and their performance and playing skills will decrease and can be easily surpassed by other players.