Other words include: meaty, robust, vigorous, weighty, ponderous . . .

I would not equate it with completeness; something incomplete might still be substantive, e.g. a chapter of a novel or an unfinished symphony. To Dennis Mazur's good list I would add "firmly rooted in reality", "important", and "concrete" (as opposed to vague or abstract). If you're just thinking in terms of quantity , i.e. the presence of a large number of the features you've mentioned, you should characterize such content as substantial rather than substantive.

Substantive content is information that is useful, may provide a new perspective, addresses the core issue of a matter, is free of irrelevant word clutter, is not a routine arrangement of boring ideas but is refreshing, easy to understand, and adds to the body of one's existing knowledge (e.g., it has substance).