>>56079855they have already progressed to easier and easier shiny hunting methods, as well as the occasional guaranteed one.
you can get an entire shiny Kanto living dex feasibly in LGPE and in Legends Arceus you can easily get all those (compared to the old full odds) if you're going for it.
in gen 4, a shiny living dex, even just a regional one, would have been an absurd and unreachable task legitimately.
if they made shinies any easier I legit would just not care about them anymore. and most people too, and GF knows this. they'd just be extra forms that don't do anything but change color, and many of them are worse than the original or hardly different. they're cool because so rare, that's it.