There is a simple solution for this. It would seem to make sense that players with provisional ratings be limited to playing others with provisional ratings until a certain threshold of games is reached. For example, twenty games. After that threshold is crossed, the provisional player is given a formal rating and access to the wider pool. If these new players are cheaters (and, many tend to be) they will weed each other out, so to speak.
It seems that the bright minds at Lichess are more concerned with banning people for having the temerity to exercise an option not to be cheated against then with promulgating sensible policies that would reduce the pairing of cheaters and/or sandbaggers with more established players.