technically they did, but the whole point of the episode was to show parenting requires both parents to do their fair share of the work. in which patrick just lazed about all day while spongebob did all the parenting and housework.
to restate, the moral of the episode wasn't that 2 men could raise a child together, but that raising a child requires both parents to do the work.
which that point can be further used to say gay men and women can raise children as long as they both pull their weight to raise the child and that the household is a nurturing environment.

I don't think Simba being raised by two men was originally questioned either.

And you have to admit that the two sea creatures are too retarded to raise a child between the two of them.