Important point of clarification, the level isn't truly impossible, a TAS proves it's theoretically winnable. Bombs5 by the same author turns out to also have been TAS, but was beaten anyway.
The issue is that if the author themself couldn't do it humanly, then the community doesn't consider it legitimate. It's disqualified, the author even came out and said Team 0% should be declared victorious.
That said, several players are still grinding it anyway. They've come too far to stop now, consider it the optional postgame superboss so we can get the True Ending. And I really hope it happens.