As he mentions in the video, the field is lagging behind other (renewable) energy sources by a few decades. Many of our energy production methods are “make thing spin fast” and then turn that energy into electricity. Coal power plants burn coal, create steam, the steam drives a steam turbine and the turbine a generator. A nuclear plant works the same way, just by extracting heat from fission instead of burning the fuel. Wind turbines, too. The technologies for this, like metal forging and casting, handling of steam, steam engines and turbines have been around for a long time and we have become experts in them. Solar panels are an exception to this as they used a different mechanism to generate electricity. Nevertheless, all of these technologies can be safely developed and deployed on land. Handling harsh marine environments up to a point where you can reliably drive these generators for an extended period of time just doesn’t exist yet. Historically speaking, this has not been necessary. So not only have to figure out how to best design wave energy extractors, we also need to get better at adapting them to the environment.