because from 1 to 4, the castles didn't change much
Except that the Knight and Sorceress moved from 1 to 2. There were no undead in 1 at all. In 3, everything mixed up and changed, only a few units remained from the previous games.
4? A complete change, really. Everything changed to the point of being unrecognizable. Heroes? Only a few.
5, on the contrary, in some ways even a return to the old... but in many ways, of course, it's new, names like Sandro, Krag... and so on appear.
also, as an example, you can take the appearance of units, buildings, objects... and it's not about 3D graphics at all (because you could have made it similar and good), but about a complete redesign
imho
The spirit is not in the form of troops and castles, IMHO.
Except the ones we've made