Blessed by who though? Without some sort of god thered be nothing for anything holy to derive its power from. That implies that just the priest himself has innate power against demons. Its the same as saying a cross can burn a demon even though god doesnt exsist. And i get its all the same canon. But itsuno has discarded alot of kamiyas ideas already to better fit his own vision. Vergil being dead/not seeing dante since they were kids, the sparda sword holding all of spardas power and being a memento to dante from his dad. Dantes own demon form just being his dads and only adopting other demons forms beyond that, he even changed the name of the store back to devil may cry. He chamged alot so its more understandabke for people to acceot the changes between kamiya and itsunos run
More than discarding he just expanded upon dmc 1, for example vergil being dead at the end of dmc 1 is not entirely true since his fate was pretty ambiguous, since the first time i saw that cutscene in dmc 1 i always thought vergil did teleported somewhere, other people think he died, official source always listed that as ambiguous
Itsuno simply revealed the answer in dmc 5, that vergil was not actually dead
The sparda weapon too being a memento from dante s father was also expanded in dmc 3 whit good explanation
So Itsuno just expanded on the world, even if things are sometimes incoherent, they can be put together if we use our imagination
Same fore vergil doppelganger
Things like This always happens in fantasy story, like in star wars, Lucas decided only later that Vader was Luke s dad, or when Tolkien retconned gollum ring from being just a normal ring whit power to be the ONE ring where all lord of the rings story is based
Retcon are present everywhere when telling a story, and they are necessary to expand the story for the better, unless you are called j k Rowling and you start writing the story you want by having everything in you're head from start to finish...
Also the holy water is probably blessed by some priest, and priest exist in dmc since we saw normal church in the anime, so Jesus Christ and his father God exist in dmc universe
And one last things, Dante fly at the end of dmc 5 prologue, to fight urizen he use devil trigger and fly directly into urizen face and try to break his shield whit rebellion, he literally stand there flying for a lot of second before urizen destroyes his sword... So dante can fly before acquiring sin dt, and as I say before dmc 2 is Canon so he can fly, but in order to tell a story you also have to not do this sort of things, and let character do stuff in order for the story to progress , same reason why Gandalf didn't fly whit the eagle and burn the ring directly, lord of the rings would not have existed
if dante would have used his power at full in every game actually every game would not have existed or ended pretty quickly, he does use his full power in dmc 2 and look what happens lol