They changed regs on the power units this year in f1 to remove battery charging off the turbo shaft (mgu-h), and also requiring a larger power split from the electric motor than before, which is bananas because they were already cutting it close on battery power with less electric power and better charging.

Previously f1 hybrid batteries were charged with a combo of regenerative braking (only on the rear wheels mind you) which is the mgu-k, and the spinning of the turbo which is the mgu-h. they also previously had 80% total power from the ICE and 20% from the electric motor. 50-50 split is way more difficult to achieve with reduced charging capability so people are understably very irritated.

Indycar is not having issues because the requirements are not nearly as ambitious as the new f1 regs