Games have been doing mechanic based boss fights ever since the dawn of gaming.
They are a safe option that companies use, it's much easier to just change the gameplay completely by putting in mechanics and weaknesses instead of creating an enemy like berial, who works like an extremely powerful normal enemy, whom you can use all your normal techniques against. Creating a balanced and challenging solo enemy like berial takes a lot of time to get everything working properly.
Even so, in my opinion the saviour was still a much better fight than any boss battle in dmc.