You are top designer at an F1 team. You've got an idea that will (maybe) make the car go faster. Say it is a different profile rear wing. So you get the lads to build one up (you have your own carbon fibre maufacturing facility on site) and you mount it on the current car and then arrange for the team to rent (say) Brands Hatch for the day, run the new wing, compare sector times, get feedback from the driver, etc - something any technical person would expect to do.
Problem: this is completely against the rules. Can't just take the car out to the track and run it between races when you want. That's why these insane chassis dynos exist, everything is a simulation now, even wind tunnel time and the number of CPUs in your CFD cluster are being regulated. This is all in the name of reducing expenses of course, but it has the opposite effect.
I saw my first F1 race in 1979, it was really something. The sport I see now has almost nothing to do with those times - in some good ways (safety!) but mostly bad (see above).
I'm out.