Why seizing the French fleet would not be simple

In a no-Channel-battle scenario, what would stop Germany from seizing the French fleet and strengthening its position against Britain?

The French fleet would fight, much of it was in the Mediterranean, and many French ships were not valuable prizes without the yards to complete or support them.

A German attempt to copy Copenhagen would be much harder than simply taking over ships in harbor. French resistance, Mediterranean basing, and the limited value of unfinished or hard-to-support units all work against the idea. Capturing hulls would not automatically create usable combat power without the crews and dockyards needed to finish and maintain them. The scenario tests a dramatic seizure plan against geography and maintenance realities.