The future is indeed never certain, but saying that the MCU series cited are single season shows isn't an assumption, they're designed that way. The examples you gave and what Marvel is doing are different in nearly every way. Traditional series like the ones you pointed out, where made in a system where they had to be sold to their advertisers in order to survive, year after year. And everyone involved in the show typically wanted it to keep going, because that meant you were a success.
The MCU franchise is a massive, multifaceted storytelling beheamoth with the might and wallet of Disn