Ending was completely justified-
1. If Gopal hadn't made the plot Aarti would have no reason to not marry Gopal..they were deeply in love, family pressure and Gopal loved her desperately which in turn made Aarti to do so..
If Gopal married Aarti and had just settled Shukla (ex-MLA) would have forced him to contest for elections which he couldn't deny because of fatherly figure. And once he won elections then he would have made him do all the scams again.. which he was not willing...
when he later had sympathy for Raghav marrying Aarti would led to a void in their friendship
Thus this was the best way he could move further in life by not harming moral ethics , and turning lives of his friends on right path