I wouldn't say those games are "totally broken". They have serious serious serious issues but that is not "totally broken". As others have noted and as Jeff puts succinctly, successors pay for the sins of the predecessor. No one will be surprised if it turns out the next AC and the Halo 5 will be less popular unless they show they have directly shown they have improved.
Someone I know in the industry also believes this and suggests when this happens they delay the "main product" and release something in the interim to build back trust. It is expensive to do but how much will that cost compared to lost sales for the next AC?