Powders are removed from w/e in creative, the reason for that was lag because they used to fall down. But now all powders stay in the air. So I don’t see a reason why you shouldn’t bring back powders(concrete powder, sand, gravel etc) It will save me so much time if you did.
theres a way to bypass it by just using #copy (a pattern).. which i'm not sure if you already know about it, but you prolly do lets be honest you're practically a legend at building. anways. thats what i use, and it's not that hard compared to having to hand place all blocks sooo. like.. i've seen you build w/ solid color blocks then use "//replace".. so for you this wouldnt be too much of a hassle or difference in your case if you don't already do it.. place the powder/sand/gravel down then pos1 and po2 it and then do //copy (your placement in position doesnt matter, only whats in your selection). then when you want to, say, replace all emeralds for whatever you had copied you can select area then "//replace 133 #copy". and then it'd replace the emerald w/ whatever you had copied. hopefully that makes sense if you hadn't known about it previously, i explained it kinda briefly... and as for the suggestion of adding it back, i think it'd be a great addition for it to be added into mcc it'd def make building in 1.8 easier if you wanted to use 1.12 blocks (since u can use 1.12 block ids in 1.8 and when u go into 1.12 they show up as those 1.12 blocks- i do it all the time), not only this, but also give more variation in builds especially if you're using simplex pattern and dont want to keep using //replace hopefully this can be added +1 have great day :D