Why do I still fail interviews after hundreds of problems?

"i'm at 800 solved, why do i still fail interviews"

Because solved count is a vanity number, and a high one sitting next to a low rating tells a single clear story: you have been absorbing solutions instead of building the engine that generates them. Contest rating is the cleanest measure there is of solving the unseen, and it is the one thing that volume genuinely cannot fake. So stop optimizing the count, because chasing a solved total or a daily streak, redoing problems you already know just to keep the number moving, and grabbing random daily problems with no calibration all feel like progress while doing almost nothing for you. What actually moves you is tracking a rating, finding the level where you genuinely start to break, living at or just above that level on problems you have not seen, and letting your weakness rather than the calendar pick your next problem. Someone with a 2400 rating from 30 contests understands problem solving more deeply than someone with 1500 solved and an 1800 rating across 100 contests, every single time.