There are several import plugins that can help you import your data from Drupal, but they may require a bit more configuration than the InstaBlog plugin that is designed for a specific use case.
Import plugins like FeedMe and Import provide you a user interface where you can map fields from your import file to fields in Craft. Assuming you can export your data into one of the supported formats for those plugins, you could map the fields from your export and use the interface to import your data.
Sprout Import is also a versatile import plugin, but does not currently have a UI. It requires that you get your data into an import-friendly JSON format, and also gives you a lot of flexibility in how you resolve relationships or handle custom data types.
Drupal Views Data Export is a good plugin to help output your Drupal data in the format that can be used by one of the above import plugins.
Extract, Transform, Load
A good process to follow as you migrate your data is referred to as the ETL Process (Extract, Transform, Load). You need to:
- Extract - Get your data out of the previous system (in your case Drupal)
- Transform - Transform that data into a format that can be imported into the new system (this can be done with Drupal Views Data Export module, or some other method that can help transform the data in the Drupal Database to importable files for one of the Craft import plugins)
- Load - Import your data into Craft (this step is handled by the Craft import plugins)
For large amounts of data, you'll likely run into several other challenges as well. Many of those questions will likely be documented by the specific import plugin you choose. When working with large migrations, while many things can be handled programmatically, don't forget to consider what can be handled manually as well. Often, a few parts of a migration are easier to do manually and being open to a bit of manual work can help make some of the programmatic steps less complicated.