As a practical matter, Israel relies on US backup in any major war - and killing Sulemani would invite a major retaliation by Iran, possibly full scale war. So it is reasonable that it would only be done with full coordination, insuring that everyone is ready.
But the time is right. The loss of Sulemani would throw the Republican Guards into disarray, right when the regime is under threat at home. He is arguably the second most powerful man in Iran, and the real force behind Iran’s gains in the region. Taking him out could be a key trigger to successful regime change - a center of gravity for the regime. And if anyone deserves to be killed, that son of a bitch does.
For Israel’s vital interest, something big must happen soon to address the Iranian threat. Now that they have secured a land main supply route from Iran to Golan, the Iranian-supplied missile buildup threatens Israeli civilian mass casualties in the looming next confrontation with Iran and its surrogate, Hizbollah. Time is now of the essence - months, not years.
Your point is well taken. However, Israel, as you know, has a truly amazing ability to successfully and effectively execute deadly covert operations.