Unfortunately they are, if enough justification exists. In WW2, both the Allies and Axis would bombard cities with civilians if those had any strategic value (military industries, disruption of logistics, sometimes because soldiers were inside the houses, etc).
Other times, it was to try out hypothesis. Germany started to bombard London to see if the population would become demoralised and demand the government to capitulate. The US sent the infamous Hiroshima and Nagasaki Nuclear Bombs, because they believed the japanese military would not capitulate through conventional means (I recommend reading more about the pacific war if you're interested, but the bottom line here is that most japanese soldiers were expected to fight to the death, and the US could not treat them like a western power. The nuclear bombs were a bet that they could avoid having to invade Japan itself)
And to be honest things didn't change that much since then. There might be more awareness of how awful it is, some countries might need better justifications than others before targeting cities, but they do it. The US did it in the middle east, Russia too, etc.
From my average joe point of view, this attack didn't target anything with strategic value, but the attack itself is a message that Ukraine can reach Moscow.
