https://en.wiktionary.org/wiki/the_grass_is_always_greener_on_the_other_sideyou don't know how good you have it, you're not missing out by using a derailleur instead of an IGH, and a coaster brake should be obviously inferior to a properly set up hand brake even if you haven't tried it, it has very clunky modulation, it can overheat on longer descents, and you can't move the cranks back to get into a proper starting position
