No one is justifying anything. Even remix songs are working and getting millions of views and likes on YouTube. The same for remake of movies.
If there is an audience out there who want to watch such movies, then it will encourage them to keep making such films as it's an easy formula to success. Why else would a HF4 or Baaghi 3 or Dabangg 3 ever be made then.
About Rohit Shetty being the greatest director, he has cracked the formula of making Hit films. Irrespective of the content, but the masses flock to the theatres when his films releases. And a remake of an already successful film makes things easier for him.
Everyone wants to make profits and they will continue to make such films. The day a majority of the audience watch content films like a Mardaani, Mard Ko Dard Nai Hota, Andhadhun and all the other smaller films, then you will see bigger stars and big production houses backing such films.
Till then the masala genre is here to stay. I am not defending or supporting anyone, but this genre is a goldmine for producers.