Funnily enough I have JUST launched a little side project that is attempting to do exactly what you are describing. (Or will do).
There's a few more features I need to add before I'd consider it MVP level and but it's getting close.
Basically you can paste in recipe URLs (so far only supports seriouseats and bonappetit) it parses the ingredient list and generates a shopping list combining everything you need to make all the recipes).
Future features include adjusting the portion size to scale up and down and combining recipes in a manner that minimizes ingredient waste when shopping