I would suggest listening to, watching and reading the accounts of the healthcare professionals who have seen first-hand what is happening. It's not about having a general idea of the concept that working in a war zone is hard; it's about the specific acts which go beyond the limits in international humanitarian law. Everyone working in such fields expects to see death and suffering. What is being reported is beyond what many very experienced people have seen before (in other wars and disasters).
Even when a country is at war, there are meant to be limits on what that means the country/ its government/ its military can do. That includes ensuring actions are proportional and necessary with the minimum amount of civilian casualties and damage to meet a necessary objective, fulfilling obligations as an occupying power including facilitating the provision of aid, adhering to rules about when people are and aren't viewed as combatants, treating people humanely when they are detained, etc. Many people are concerned about the multiple reports, including statements from the Israeli leadership, eyewitness accounts, satellite images, etc., which indicate that the current actions of Israel aren't within those limits. Many people are concerned about what it means on a wider level, too, that these limits no longer seem to have to be respected. The limits existed to protect everyone, and the world as a whole is less safe without them.