The biggest problem right now with Starship is the heatshield problem. If it's a one and done flight it's actually still worth it but full re-use without solving the heat shield problem is not actually possible (right now). It turns out slamming into Earth's atmosphere at orbital velocity or higher is one of those things that pretty much every material we've thrown at the problem has had problems being used forever. We need to do experimental flights in order to provide more data to materials folks working on this. Honestly I respect the hell out of anyone working on this problem because it's the next big tech hurdle we need besides landing a booster. And this one is still not solved.