I made a review of the 3 cars before and what RB need to solve with RB21 to get back on top
There are inks to individual threads for major aero components too on RB cars. As for RB21, these are 5 major topics in my view
massive improvement of suspension system, with the biggest accent on reducing front suspension stiffness without losing high-speed stability and performance
further improvements on the floor in order to reduce low- and medium-speed performance gap to the front, as well as getting back to being the class-leading design in terms of stability and driveability
find a different innovative sidepod development direction to open up a new path for the final season of this regulation cycle - maybe even take some inspiration from McLaren?
increase the front wing load in low-speed section and utilise the flap-flexibility at leas as much as McLaren and Mercedes
work closely with Honda to get back on top of reliability issues that cost them the win at Spa this year