There is a MV3 based uBlock Origin and it works in most cases. See https://github.com/uBlockOrigin/uBOL-home/wiki/Frequently-asked-questions-(FAQ)#filtering-capabilities-which-cant-be-ported-to-mv3 for known missing things. Could you explain your "completely impossible" within that context please?
@waldi
MV3 only allows for list-based blocking, rather than the dynamic pattern based blocking used with MV2. Initially, Google tried to completely prevent any dynamics with those lists and severely restrict their size, though they later realized they wouldn't get away with that. However, the current specification still makes it very likely that any blocking will miss stuff.
@bobpony