> It's happening anyway and it's not like you can siphon the hydrogen off and do anything else with it.
Actually this is another megastructure process known as Star Lifting. And it's not just hydrogen you can siphon off - the sun, by virtue of its immense size, contains the overwhelming majority of every element in the solar system.
Unfortunately because they burn up so quickly, the hydrogen isotopes we would use in fusion reactors are actually incredibly rare in the sun. The sun is estimated to have about the same amount of deuterium as Earth's oceans. On the other hand, Helium-3, another potential fusion fuel, is very abundant - about 10-20 Earth Masses are present. Still though, burning all this helium 3 at the same energy production rate of the Sun would only last us 870,000 years - a drop in the bucket compared to the lifetime of the sun.
So what if it's inefficient? It's happening anyway and it's not like you can siphon the hydrogen off and do anything else with it.
What kind of purism is it to not tap the largest energy sources in existence because you bristle at their inefficiency.