I see that argument and I want Ukraine to win quickly too. But if you follow that logic then there are lots of other weapons we could be sending them. I find it hard to make a case for sending them cluster bombs that wouldn't apply just as well to sending mustard gas, nerve agent or tactical nuclear weapons - the use (or even possession) of any of which could improve the effectiveness of Ukraine's defenders too. But the point about all of these weapons - including cluster bombs - is that civilised societies have decided that certain weapons that cause mass death and destruction are not appropriate to use in conflict no matter the scenario.
Globally, the victims of cluster bombs are disproportionately civilians, with a huge proportion being children. All the fighting currently is happening in Ukraine so it's Ukrainian children who are going to be getting blown up by these for decades to come after the war has ended.