Ansu can still be a top player, World Class even. This is a hamstring injury so not a career killer. Eto'o had his meniscus removed at a young age too and Robben suffered injuries a lot until he moved to Bayern and got a consistent run of games without breaking in half.
But yeah perhaps time for people to take a step back when it comes to Ansu. He's not Messi. Never was. Nor someone the club will build the team around, that will be Haaland if we somehow manage to sign him. Barca simply have to find a way to sign a player like Haaland or else this rebuild is going to last a few more years. It's tough to compete for major titles unless you have at least one super elite player.
I am not saying that he is 100% certain to fail or have his career ruined due to injuries.
But realistically, let's say it this way:
1. do you know how 90% of La Masia kids turn into nothing?
But of course, 1 out of 10 turn into Puyol, Xavi and similar.
But when you see the next La Masia kid, he still has 90% chances to end as a nobody than to be the new Puyol/Busi.
2. well, imo, the same is with Fati in terms of injuries.
This Robben example is mentioned all the time here. And young Messi with muscle injuries.
But on every Robben, there are 10 guys who's careers turned into meh after injuries in the early days.
So, yes, he might be the next Robben who will overcome injuries.
But also, he is more likely to be in those 90% of guys who's careers were ruined or who's development was hindered a lot.
In terms of development, he was a kid who played at the age of 17 and in the future he might be a player who is 22 years old and barely had more than 10 matches in each of his senior seasons.
That is a lot of experience, chemistry, learning lost.
A huge part of a theory "he is young and has potential, he might improve a lot" will go down the drain.
Look at Dembele. He is here for 4 years, he had tons of injuries. Has he improved even one bit since he came here? No.
More or less, his career and development were frozen in time because he never had a chance to play a full season, to learn and grow.