No, quite the opposite. Gantz is considered a moderating force in the coalition who probably prevented a lot of Palestinian deaths due to his measured approach. His main point of pressure was that Bibi has absolutely no plan for transitioning to a post-war Gaza. Someone will have to be in charge of governance and reconstruction, and that plan has to begin now. Bibi has avoided the question because there is really no good option. It’s politically savvy to let the situation devolve further into crisis.
Gantz leaving weakens Netanyahu but also strengthens the far right ministers. In the short run, this is probably a bad thing, but could be good if it triggers new elections and ends Bibi’s career.