That goes for any unexploded ordnance, we are still cleaning up regular unexploded shells from World War 1 more than 100 years after the fact and every now and then it still claims a victim.

It sucks, but you have to offset that against the benefit. The longer the Russians occupy parts of Ukraine, the more atrocities they are able to commit against civilians (cf. Bucha, Irpin, Izium, Kherson,...). Also when people talk about the civilian casualties, they always forget that the bulk of the Ukrainian soldiers were civilians just over a year ago, and they would love nothing more than to return to a peaceful civilian life. Their lives are valuable as well and should be protected too.

If cluster munitions helps them to get rid of the Russians faster and with a lot less casualties, it is a trade off we should make.