I noticed that many buildings have joint edges with roads and other landuses.
Likewise lines showing rivers/streams/ditches and roads with landuses.
It is much more logical to me that roads and building areas are separate, since they are not really overlapping in reality, just next to each other. They belong to different groups … Much easier to edit, easier to visualize, easier to handle.
Therefore, you should avoid such connections, and those that are have joint edges, disconnect as far as possible.
In JOSM “G” (Unglue edges).
Also use “Q” (Orthogonize shape) to make all angles 90 degreese for buildings.