Were France's LN.401 and Br.810 underpowered?

Is it fair to call the LN.401 and Br.810 underpowered?

Not categorically: the LN.401 had planned power growth, and the Br.810's final engine fit never became certain.

Only a small batch of about fifteen LN.401s preceded the more powerful LN.402 development, so the initial aircraft was not necessarily the endpoint for French carrier dive bombers. The proposed engine increase discussed is from roughly 690 to 1,000 horsepower, although even that remained modest for a carrier aircraft's added structural weight. The twin-engine Br.810 derived from the capable Br.693 and shed some forward armament to offset naval equipment, folding wings, and a torpedo load. Its likely performance depends heavily on whether France could produce enough domestic engines. American radial engines are raised as a plausible substitute, although the unbuilt Br.810 never acquired a settled wartime fit.