Stories like that of 'Bhonsle', even though fictional, are as real as they could be in bringing the common social tensions of Indian lives upto the fore.
Bombay's birth was pursuant to colonial imperatives of the British rule. The Britishers wanted to set up an industrial city that could help them expand their international trade in textiles. Bombay's choice happened to be a natural one because of it being a port city. In the wake of its industrialization during the British Raj of the 18th and 19th century itself, Bombay has acquired cosmopolitanism, not because of fancy urbanity, but because of its need to draw in people from different parts of the country to serve as hands towards propagation of past imperial designs.
As far as the city of Bombay goes, no one can really lay claim to the city, as everyone has had a role in its shaping and formation. However, after the reorganization of Indian territories along linguistic lines, Bombay fell into the state of Maharashtra, which was formed as a political expression of the 'marathi' community.
This sense of 'marathihood' now seeks to cannibalize Bombay, a city of its own, with a larger than life background to its emergence and existence. This sense of marathihood intends to re-form Bombay as an imagination of the marathi expressions, and in this urge, perhaps, the origin stories of Bombay's cosmopolitanism is lost.
It's still debatable whether it'd be apt to call Bombay as the cosmopolitan city, and Mumbai as the super-imposition of 'marathihood' - something that 'Bhonsle' intends to portray. The juxtaposition of the frenzied crowd revelling in the streets around the Ganpati festival, with a traumatic event in the storyline betrays the director's desire to associate 'marathihood' as an expression of mob frenzy. This is nothing but coloniality, because it imagines Bombay's cosmopolitanism as a victim of 'marathihood', when a decolonial reading would imply the sea crawling back to claim reclaimed lands, i.e., the natives reclaiming ownership over the city's destiny.
Because the imperial rule ended up designing Bombay's life, one could say that the actual natives never got an opportunity to claim ownership over the shaping up of the city. In that sense, one can say that 'Bombay' will be forever lost to 'marathis', if they give up their claim on 'Mumbai', the marathi alter-ego of the city.
Sadly, Bhonsle, reeks of post-colonialism, because it does not intend to disturb the colonial legacy of Bombay's cosmopolitanism, while at the same time, the film wants to delegitimize the discontents of natives, who are unable to interact with a city of their own, but which feels as much alien as a foreigner. In castigating 'marathihood' the director chose a simplistic route of vengeance towards a denouement that could be subject to multiple interpretations as per one's personal taste.