I'd argue that the ease of digital manipulation has led some studios to do what you say - postpone creativity until after the movie is mostly shot,

None of this is true. You can't shoot plates and do whatever you want later. Even basic effects shots take intricate planning. They were talking about cleaning up mistakes and small details.

which leads to that design-by-committee feeling

I'm not sure what this means in the context of a movie but it isn't how movies are made.

There are art directors, production designers and vfx supervisors and they answer to the director. Movies are the opposite of design by committee. It isn't a bunch of people compromising, it is the director making decisions and approving every step.

that sense of 'don't worry, we'll fix the lighting it the editing room'

This doesn't happen because it isn't how anything works. You can fix lighting in editing.

the same sloppiness as 'and then the big gorilla will use his magic attack and it will look really cool,' without any thought given to it's actually going to look like.

Enormous thought and planning is given to every stage. This idea of not liking lots of effects in fantasy or comic book movies and then attributing that to sloppiness or apathy simply does not happen in big budget movies. There are multiple stages of gathering reference, art direction and early tests, many times before any photography is shot.

If you procrastinate making artistic decisioms for long enough, there's not actually going to be any art in the movie once it's done.

Not only does this not happen, it doesn't make sense. Just because you don't like something that doesn't mean huge amounts of work and planning didn't go into it.