Autocart has been removed as a separate feature in MCM 2.0.
To simulate the old Autocart behavior, edit the config.yml and set EmptyFrictionPercent and PassengerFrictionPercent to 0. Also set SlopeSpeedPercent to 0.
With those 3 settings at 0 minecarts will move at constant velocity.
You may also wish to set MaxPushSpeedPercent to 0 to prevent Passengers from pushing the cart.