Starship's Belly Flop Maneuver
everydayastronaut.com
everydayastronaut.com
I can't see this ever being approved for human flight without major seeing changes.
Even if the design is fully proved out and works flawlessly, the reliability numbers behind the Raptor engine just aren't there yet.
...major design changes.
You see, the failure modes are different with winged designs and active propulsion landing designs. Winged designs, in the extreme, can safely land with zero control after being pushed from orbit - in case of low Earth orbit, just decrease speed by about 200 m/s and that's it. Aerodynamic of the spacecraft can be designed so that the spacecraft will passively stabilize while going through atmosphere, and the terminal velocity could be low enough that even wheels deployment failure won't be lethal. That's not to mention designs where the parachute is opened on orbit, allows going slower through atmosphere and landing - vertically - with low speed (some information is here - https://www.nbcnews.com/id/wbna6714639 ).
At the same time deploying parachutes is very much an active operation - failure of which costed Vladimir Komarov his life. Engine-supported landing was once considered in 1980s in USSR and declined on the grounds of safety; in comparison, Buran flew fully automatically on the first attempt. Today's systems are unquestionably better, but with engine failure there is little time or possibilities - unless something unusual would be invented - to compensate.
Comparing Dream Chaser and Crew Dragon, I'd definitely consider the first one as inherently safer design for landing.
The requirements for anything beyond a simple Moon base really are quite daunting but we will never get close without taking a much riskier approach to space than we are seeing now.
Why won’t Starship have an abort system? Should it?!
https://everydayastronaut.com/starship-abort/
Video Version:
The Raptor is very new engine, it will be mass manufactured at a large scale and will have 1000s of firings. That will prove the reliability eventually. They will also have redundancy on the vehicle.
Longer answer: not quite everything, but Mars conditions are significantly different. Gravity is lower and atmosphere is less dense, so terminal velocity is different, reaction to wing motions is different, engine thrust required to negate the gravity is different; all of that will at least require changes to the control algorithm and testing, at most will ask for redesign of some mechanics.