You would not "marginally improve", you would dramatically improve. That's the dirty secret of these interviews they are not that hard to get good at. There are

You would not "marginally improve", you would dramatically improve. That's the dirty secret of these interviews they are not that hard to get good at. There are at most a little over half a dozen data structures and about a dozen algorithmic technique patterns that show up in these interviews, once you do enough of those types of problem, you get better at it. I am willing to bet that spending an hour every day on leetcode you can probably be good enough to pass interviews at most companies in a month or two (assuming you had exposure to DS and Algorithms in college, if not add more time but the general idea applies). Maybe not Google but I would bet you'd be good enough to see double digit increasing in your onsite -> offer conversion percentage. Whether that would be worth it is a different question, the answer for many people who already have good jobs is no.