F1 cars need wings for advertising. They also need a certain amount of downforce to be competitive or superior to other open wheel formulae.
Downforce needs to be cut back to something like one metric ton or 10,000 kN in order to limit the aerodynamic influence. This cutback must be achieved by measures that will not allow the designers to claw back downforce. One could use standard components or legally limit downforce. That is not really important.
Mirrors need to be fixed to the body of the safety cell and must be vibration protected. The nose design must allow the driver to see the whole front end of the car. Nowadays drivers simply cannot see the front wings which is silly and not safe.
Mechanical grip should be further increased by wider rear tyres like those in the eighties and early 90ties with a width of 450-500 mm. Tracks should also be increased back to 2000 mm from 1800 mm now. The cars looked like proper racing cars then.
The main thing is discouraging sterile aero engineering and go back to finding competitive advantages from efficiency improvements in the drive train, better suspensions and electric technologies. This will not only help the show but also get more manufacturers involved.