Bartender 4 is great for that, when you have a target it will tint the spell red if it is out of range.

Try the Grid + Clique combi, Grid is a raidframes addon, Clique is a click-to-cast addon. I've used that combi for raid healing for years already. Both are really lightweight and highly configurable.

If you want to keep it simple, you can try Chinon.