XCOM has actually grown more hard-hearted about such things over the past two decades: these days, the maps haven't had all the civilians conveniently evacuated beforehand and collateral damage is still not a concern. Otherwise, there appears to be no downside to reckless explosive use. However, I've never actually blown one up to test that.
both explosives and stray weapons-fire can potentially break them), and further presume that any which are destroyed will decrease your end-of-mission reward. I presume that they function similarly to any other cover object in terms of being destroyed (i.e. Central calls out specific cover items the first time you encounter them in one of these missions - similar to the 'please don't break that' messages for Power Cores/Flight Computers in EU/EW - which look like some kind of glowing crate in a metal frame. There are also supply raid missions which give an explicit objective to 'not destroy critical supplies'. (Not all enemies will drop rewards at all, and killing one which would have triggers a 'loot destroyed' popup on the lower left, so if you don't mind save-scumming you can entirely avoid this and still blow up ADVENT left right and center.) The primary risk with explosives is losing a yellow timed-drop reward by getting the killing blow on an enemy with one - similar to losing weapon fragments in the first game.