Infill housing is the process of building a new house in an older neighborhood, typically by tearing down an existing home to make space.
A common problem with infill housing is how new constructions tend to overpower their older neighbors.
The challenge with infill housing is to have the spaciousness and the amenities for modern living while avoiding the bloated look of McMansions (which are okay in the suburbs (McPlantations) where every house is one. But to build one among older, more refined homes, not a good idea.)
Furthermore, as Christopher Alexander wrote in A Pattern Language, when you have a nice piece of land, don't choose the prettiest spot to build on, but build at the ugliest where trees and grass don't grow, use architecture to improve the beauty of the land.
Such should be the attitude with infill housing. Look for opportunities to improve a setting. Avoid disturbing an already good one. Don't replace a good old house. Replace a neighborhood eyesore (yes, even old houses have poorly built ones), or build on a neglected/busy street to improve it. Or better yet, be the first to tear down a McMansion :-).