The problem is not that there isn't enough tidal power. The problem is that the pentland firth is both fast enough and deep enough. Orkney alone probably has enough tidal power to serve all of Scotland's needs, but most of the tide races are no more than 5 meters deep. The meygen turbine has a 18 m diameter so it's hard to find places that can support it in a way that doesn't pose a danger for surface vessels but also has a current fast enough to generate a meaningful amount of electricity.

100 percent accurate because building benthic structures is incredibly hard. Having one with moving parts is even more crazy.

For sure, but meygen is way too big for most fast moving tide races. And most places that are deep enough don't have a fast enough current. The pentland firth is unusual in that it is both deep enough and has a current in the order of around 10 - 15 knots in places. It flows like a relatively fast moving river. It's not a normal stretch of water.