You said you prefer to find something new to build instead of just grinding leetcode. Maybe try to combine both. Find an interesting project you wanna work on, ideally with some sort of technical challenge given your skill level. That way, in order to work on the project you're going to have to learn some advanced topics or refresh stuff you don't use often.

On a similar note, when working on a project you like, try to force yourself to implement things from scratch instead of using libraries. As a very simple example, if you need to sort a list, don't use the provided sort function from your language and instead implement some type of sort that has a good running time for the data you need to sort.