What is the main disadvantage of fusion?

Can you elaborate on the primary drawback of fusion energy? I understand it's a promising source of clean and abundant power, but surely there must be some significant challenge or limitation that researchers and engineers are grappling with in order to harness its full potential. Is it the monumental cost of building and maintaining fusion reactors? The incredibly high temperatures and pressures required to initiate and sustain the fusion process? Or perhaps the complexity of managing the radioactive byproducts and ensuring safety during operation? I'm eager to gain a deeper understanding of the main disadvantage that stands in the way of widespread adoption and commercialization of fusion energy.