"You don’t need a architect to build a house, but it doesn’t mean that you will make the right decision when building it."

True. And the same is true for a software application.

"If you have the knowledge to build it but you are not an architect, a title is just a title."

False. Architects are not primarily builders, we are thinkers, planners, coordinators, communicators, etc. That's why there are different titles. These words have meanings.

" ... to construct a city you probably will have an architect, at least if you want to build a sustainable and scalable city."

Buildings and applications should have architects. When they don't, as you point out, they can turn out ugly and dangerous.

Cities have city planners that coordinate the major, shared services and systems (e.g. power, water, waste, etc) and the efforts of all the building architects in order to create a scalable, sustainable city.

Bom domingo! ;)