If that is true, then virtually no one can do good philosophy at all, because absorbing all the prerequisites will take a large portion of most people's lifetimes.

It doesn't really take that long to learn things. But good philosophy already looks like this - my favorite political philosophy professor threw out references to computing, physics, history, etc. assuming students would get the references or look them up. Much like pride is the crown of the virtues, philosophy should be the crown of the sciences.