Is it bad form to always target the concentrating wizard?

One of the most useful things a wizard can do is lay down a concentration spell that affects the entire battlefield. However, a "tactically" minded enemy knows this and as soon as it happens would want to get rid of whatever concentration effect is currently active. This means that they will want to either use their ranged attacks or close the gap with the wizard to break that concentration.

I know a lot of people very much enjoy a style of play where enemies always behave intelligently because it's both challenging and "realistic", but I worry it makes the game not fun for the wizard player. Essentially it makes it so that if they do their job then that inherently draws all eyes on them so they're constantly being attacked, and they're the class least suited to being attacked.