The most straightforward way to populate information into the accordion for each individual product is indeed to create and assign separate product templates, however, we understand that doing this to a lot of products is tedious work.
A bit more automatic way would be to use Shopify's built-in metafields - https://help.shopify.com/en/manual/custom-data/metafields.
Follow the steps in the documentation to set up a metafield for products, for example, Ingredients:
Define the metafield content in the specific product editing screen (all the way down!):
 
In the theme customizer, navigate to the Product template, select or create the accordion you want to add the information to, and select the metafield you created as the "Dynamic information source" by clicking the icon above the text field you want to populate.
This will automatically pull in the information from the product metafield definitions into individual product pages without having to create separate product template for each one.
