You can easily build things like social media platform, e-commerce solutions, project or product management tools, CRMs, inventory management solutions, messaging/chatting service, most types of marketplace.
How i see it is, you can pretty much build all sort of app where you storing some data from input and then reproducing it on command with some rules applied.
It depends on low-code platform, some of them are more focused on specific use cases such as approvals and workflows, while there are few with possibility to write your own code or use external libraries.
In this case you have flexibility similar to classical programing and it is up to you decide what advantages will low-code get you.
In general games, firmware, operating systems, and complex calculations are easier in classical programing or specific frameworks.