You do realize that this is not true for every place Luffy visited? In Cocoyashi, he did not destroy the town, but the place Arlong resided; in Syrup Village, the village wasn't destroyed; In Skypiea, Luffy prevented the destruction of the country by taking down Enel.
And for the ones that's true, good lord.... you're corrupting it so much that you're missing the point.. Places are destroyed, yes, but the
people's happiness and freedoms return.. that's the point, and that is more important than buildings that are destroyed in the country.......
Luffy simply witnesses all the atrocities in these places, and he
chooses to do something about it. Luffy is the only one who could
do something for the people there; the people are powerless, so they depend on him...
Orange Town --> Buggy strikes fear and tyrannizes the local inhabitants. Luffy does something about it and he succeeds; Buggy is defeated and the place is destroyed. But the inhabitants rejoice.
Alabasta --> Crocodile plots to take over the country and be its King, by sheer deception. Luffy does something about it and Crocodile is defeated; everyone learns the truth and the inhabitants rejoice.
Fishman Island --> Hody strikes fear and tyrannizes the inhabitants, even killing people who signed Otohime's petition, and tarnishing the good name of Otohime and the royal family. Luffy does something about it, and he succeeds. Fishman island's inhabitants rejoice, as Hody is defeated.
Dressrosa --> Doflamingo strikes fear and tyrannizes the inhabitants. Luffy does something about it and he succeeds; Doflamingo is defeated and the country is destroyed, but the inhabitants rejoice.
Do you see a pattern? Yes, the country in some cases is destroyed, but
the people rejoice and their freedoms return. It doesn't matter if the country is destroyed, it's the people that's important. Recall what Vivi said in Alabasta, in chapter 187.
"Please destroy this palace"
"The kingdom of Alabasta is its people. Because of them, there could be a country"
Same thing King Cobra himself said.
What's more important? Buildings that have a 4,000 year old history, or the people that have served the country. For Vivi and Cobra, it is the people.. and for Luffy, it is the freedoms for these people that are important, not the buildings. The destruction of the infrastructure that served the country, and its aftermath represents a new beginning for that country to start over, but with people's freedoms enjoyed.
Gatz message to the people when Doflamingo was defeated was exactly that: "
All that can be seen outside of the cage... is just a ruined town? or free land not controlled by anyone anymore?"
And Oda's message via the narrator itself was also that: "
A collapsing country is not necessarily an unhappy one -- this day, the people of the country wept with happiness in the middle of the ruins.."
Heck, even Kyros' flashback speech above, is fitting here.