It will take the same time regardless of the income as there is only one dev. Also this is a side projest so that may be the reason it takes as much time.
There are a lot of games with only one devloper and low content updates,but they have a lot of subs. Luck and skills both are a factor of your success. A good combination of both will get you anywhere. Or you can just make a NTR game and get a shit tone of money😅.
But as I said,this is a side project where he practices his game making skills in unity engine ,but his main project has a team for the devlopement.