The basic thinking error with the usual methods of trying to imitate the fusion processes on the Sun and the other stars is that they consider the Sun as an ordinary ball of gas. A ball filled with hydrogen, helium and many other gases. But it is not like that. It is not gravity and temperature that are decisive.
The sun and the other stars are plasma balls or plasma spheres filled with an electrically conducting plasma that swirls, creates sunspots (the sun's own "black holes"), electric currents, that circulate, flame...which causes deuterium, tritium, etc. can constantly clash and collide. And thanks to these ongoing processes also being catalysed, controlled and regulated fusion processes are created that produce the heat and light we can constantly see coming from the sun.
We can imitate these processes here on Earth if we learn to control and regulate the fusion with the help of catalysts and computers!