IMO it's not the issue of the city. It's the issue of the living space. Humans were originally hunter-gatherers that lived in tight knit tribal communities with intimate shared spaces. Any living style that deviates from this will induce loneliness.
To eliminate loneliness you must form tribes. To form tribes you must produce settings that promote tribal gatherings. In essence this means intimate shared living spaces with medium sized groups of people. The keyword is "medium-sized" humans are not use to living with huge urban shared spaces where the people you see on the street everyday are different.
Gotta choose the right tribe. Bonds are usually formed through forced interactions. You have some choice but it's limited.
Few people have the power to be friends with anyone they want. I wish i could be friends with Bill Gates or Elon Musk, unfortunately it's outside of my abilities.
To eliminate loneliness you must form tribes. To form tribes you must produce settings that promote tribal gatherings. In essence this means intimate shared living spaces with medium sized groups of people. The keyword is "medium-sized" humans are not use to living with huge urban shared spaces where the people you see on the street everyday are different.