No, you're not a bad mum. Lots of adults find playing with young children boring. Let's face it, adults don't play with toys, it's not our thing.
But, for young children, it's important for their development that they interact with parents and other trusted adults.
Try factoring in daily activities such as walks, where you are pointing out things along the route, or if it's fine, a walk to a park where you can sit baby on a rug and give him some toys?
Even getting him dressed can be an activity, with you telling him the names of the clothes as you dress him.
Cloth books are a good idea too, where he can engage in trying to turn the pages while you talk about the pictures.
Or mum and toddler groups where the activities are organized, and you both join in.