Why do you think its broken?

You do know, having played the game, that in some situations (standing stones and abandoned farms) the boars found there are tethered to those locations so even if you are able to tame and get them to your base they will, if they escape, go back to where you found them.

Other boars are not tethered, but if they escape and get spooked they will run off (jut like tamed wolves can move far away from their 'stay' point if they start to chase/chain kill mobs in the area).

And why would you expect boars to follow you like tamed wolves? By taming boars you are preventing them from being scared of things like fire and making them passive to you. They are not meant to be companions.

Also you can always harpoon them if it is that problematic.

But just because tamed boars do not behave like YOU think they should does not make the mechanic broken.