People say fusion will offer unlimited cheap energy but fission can already do that, its just not psychologically satisfying because uranium is not perceived to be as abundant as deuterium even though its functionally unlimited on the basis of a normal "non kardashev" human civilization. If fusion gets developed but it turns out a fusion reactor costs 10 times as much as a fission reactor it won't be used, it doesnt matter if the fuel was infinite and free.
There's nothing you can do with fusion you cant do cheaper with fission.