No matter what the developers come up with, failure is almost guaranteed. The fifth installment is weaker than the previous ones because almost all of the heroic spirit is stifled by a purely commercial project, and yet another fifth game with additional features is a complete departure from the great series.
Each step from King's Bounty to Heroes 4 is a whole revolution and evolution. But there is a limit to the number of such steps, and not every company is capable of making them. The first four installments can be considered full-fledged films, and after that, it became a series based on the same concept.