Greetings!
First of all, you have written a very good post full of truths and issues many folks here can relate to.
There are a lot of massive "constructions" out here on PMC that are supposed to be buildings, but the enormous size and the over-detailed facades make it look like a huge mess, especially in vanilla minecraft. Unfortunately this is an issue that many beginners fall into. They think they have to build gigantic to fit as many details as possible into their construction, but this is a massive fault! I did so too on a few builds and the result is not worth to mention anymore.
Over the years I could gain enough experience to actually come to the conclusion, that less might sometimes be more. This also relates to the point where you write about the scale, or size. Inside our team we have defined 1 block as ca. 70-80cm which results in a very realistic sized scale fitting with the size of the minecraft character. Anything smaller than this, is very hard to detail and most of the bigger scales are just too big in relation and proportion.
In conclusion, I can only agree to your points. It is indeed necessary to keep things small in order to preserve realism. And that also includes fantasy styled builds. As you said, oversized buildings might look good on renders, but in-game they are mostly not very useful, unplayable and too big to see it in all of it's extent.
Keep things small but realistic, playable and useful.
