This issue is discussed in the forum quite often, which shows that it is in fact a problem for many players. It is just annoying having to wait until the time runs down just because a player didn't resign properly.
I somewhat agree with @ricardo-sf that with certain heuristics lichess should be able to do a better job on this issue, but as a side note, maybe it could also do a better job supporting players to identify such people:
Currently there is only the possibility to notify the moderators in a rather unspecific way about players that are cheating or insulting others.
Why not add the possiblity to notify that a player left the game without resigning? After a certain amount of such notifications the player could be blocked automatically. I'm rather sure a human should be able to understand if an opponent did it on purpose (for example after losing an important piece) or it was just a disconnect.
I somewhat agree with @ricardo-sf that with certain heuristics lichess should be able to do a better job on this issue, but as a side note, maybe it could also do a better job supporting players to identify such people:
Currently there is only the possibility to notify the moderators in a rather unspecific way about players that are cheating or insulting others.
Why not add the possiblity to notify that a player left the game without resigning? After a certain amount of such notifications the player could be blocked automatically. I'm rather sure a human should be able to understand if an opponent did it on purpose (for example after losing an important piece) or it was just a disconnect.