Compare the size and proportions of the new Indycars, with their more "sportscar / roadster" feel.
Obviously there's a big technological difference.
But, just for comparison and discussion, here are some basic specs I looked up -
The Dallara Indy chassis has a wheelbase of 117.5 to 121.5" (the range being different configurations for different tracks).
Weight: 1600 lbs (driver not
included, so 1750+)
2.2L twin turbo V6
A 2019 Formula 1 car varies by manufacturer, but these are basic parameters -
Wheelbase: 142.5 to 147" (20 to 30" longer
A new rule allows a bit more fuel to avoid boring mileage strategy, but that means more length for tanks as the fuel must be within 400mm of the longitudinal centerline.
Weight: 740kg or 1631 lbs, but 80kg of that is driver and/or ballast in the cockpit.
Mercedes has a very long chassis, which they feel gives extra body surfaces to generate downforce, and they feel this outweighs the the extra weight and lack of cornering agility.
Ferrari is experimenting with a longer transmission and axle design to move the engine farther away from the rear wheels. However, weight distribution is regulated by the FIA (why??), so the front axle would have to move forward.