You're not to think of them as blood elves, but as night elves because that's what they are you're to see a side of the night elves that has been put on hold to fulfill a task. This is not dissimilar to the high elves at all, They are elves, not a separate race.
The difference with high elves and blood elves is their brighter look and their cultural diversification from the night elven group.
they dropped the night stuff.. this is why you have Highborne night elves and highborne high elves - one group is not changing their identity, the other does.
So you look at the high elves/blood elves, brighter colours, brighter architecture, day themes, sun themes - you are to contrast this with the night elves which are the original but a contrasting theme, night instead of day, nocturnal, moon instead of sun, the architecture is similar ofc, they're elves - when the normal night elves made an attempt at building a city, you can see similarities to it in Blood elven architecture, in fact when the high elves go all rural, they use night elven rural architecture, when you saw silvermoon city it had some semblance to the night elven architecture you saw in darnassus which was just a smaller temple model.