While Jakku sufficed as an unfriendly environment for Rey to become self-sufficient, this junk world would have been a more unique offering to the Star Wars universe.
Tatooine has been featured in four of the live action Star Wars movies, so audiences are already familiar with how tough it is to live in such a climate and how much sand sucks.
A junk world, on the other hand, is something that hasn’t been seen yet in any of the movies, and while Jakku had its fair share of garbage laying around, it’s not the same as having an entire planet that’s cluttered.
Having so much junk certainly would have made Rey’s life easier, as there would be a lot more trinkets and knick knacks for her to trade or fix to use for survival.