This is completey my opinion and the names used don't represent any significance in real life , if any scenario is there where real life people names match is purely coincidence (inspired from Dhurandar)

After shahrukh khan or i would better say the three khans there haven't been superstars . Hrithik, Ranbir , Ranveer , Allu Arjun , Yash , Vijay they are all great stars . 
But still the kind of fame in terms of number of people Dilip kumar , Rajesh Khanna , Amitab bachchan, Shahrukh khan , Salman khan , Rajnikanth experienced
There used be a single top most face
Ofc everyone had very different era and extremely different reasons

I would Say it's because of the Uniqueness of their personality, acceptance of their personality and the kind of self Own ness they had (Embracing their own self uniqueness)

Srk became a star when the previous bollywood star amitab character was so much blended in masculinity and male Centric audience. Ofc from 1990's there were romantic movies experimenting with Bollywood but with Ddlj , Srk charm , Acting he broke away perception towards women and love in a rigid country like India .
Salman was a star At the same time as Srk, okie initially he had female fan base but after his so many controversies he lost it , he may have builded his male fan base again but there aren't many women who likes salman khan whereas Srk as male , female , children all of them liking towards him. I think that is one of the reasons why Shahrukh's popularity is more than salman khan

Ig this is why
Ranveer Singh did Dhurandar a politically biased film people 10 years later will see and think it will leave a bad image of him as They won't have seen the craze of the movie and would think purely for the movie

Same goes for Aditya dhar
He won't have Dhurandar making him fans even 15 later years but swades has been making fans if Srk even today . people are loving Aamir Khan even more cause of his filmography like PK , same with Rajamouli I think he will go longer as he is even more focused on universal themes while completely owning his roots 

My take on why stars currently aren't reaching people's heart as deeply as the previous bollywood biggest superstars