You’ll never regret choosing something you want to work on. Especially when what you want to work also makes money like energy or AI.

Also, these fields are not evil or useless like weapon design or hedge funds. They are actually useful to society, so you feel like contributing to the general good.

Don’t worry about healthcare, there are thousands of people who work on healthcare.

And, if I may, if you did work on healthcare, your very own contribution to solving this problem would most likely be very small. Unless you somehow become the Elon Musk of healthcare... which you know, may or may not happen.