Unless you're a competitive bodybuilder, hitting the gym shouldn't be an hours-long time suck as you painstakingly isolate each of your 300-ish skeletal muscles. No one has time for that shit.
And if you make time, I question your priorities -- you don't need to add three sets each of preacher curls, hammer curls, barbell curls, and concentration curls after you've done alternating biceps curls. Go home, spend time with your partner or your cat. Surely one of them would like to see you.
As an exercise physiologist, I hesitate to say any exercises are "bad," because there's no such thing as a "bad" exercise; there are just bad exercises for certain people, and there’s certainly bad form. But if you’re having a hard time making your workout a priority, you need to ditch the exercises that isolate one or two muscle groups and focus on compound, multiple-joint movements that deliver more bang for your buck. Your partner, your cat, and your body will thank you.