Yes! You are correct.

Rotenone blocks NADH from being able to transfer its electrons to UQ in complex I. However, succinate is still able to transfer its electrons to UQ via complex II.

The problem is that every turn of the Krebs cycle produces 4 NADH molecules and only 1 succinate. Not being able to use the NADH electrons severely limits the electron transport chain and dramatically slows the production of ATP later.