What your asking for would make breeding and eving to simple. You're supposed to work for your super strong Pokemon
Yeah, I don't mind some of the breeding quirks. It's mostly junk like Natures being permanently set and Heart Scales not giving you full access to a Pokemon's natural move list that bothers me. If you bothered to breed an Egg Move onto a Pokemon, you already know what you want and have no reason to delete it, but for stuff like getting Spore on Breloom? Because Breloom magically can't learn Spore once it evolves? That's silly. The fact that you can permanently miss a chance to teach a Pokemon a move it naturally learns because it evolved is just lame to me. Sure, with something like Roserade, I can deal with it because it evolves by Stone, but Breloom? Something that evolves naturally? That's pretty dumb.
Natures I mostly want to be able to change just because of soft resetting for Legendaries. There is no "work" involved in getting a perfect Legendary, just a bunch of tedious nonsense that has nothing to do with actually playing a game. It's a totally unnecessary brick wall between you and obtaining a plot-required Pokemon. Rayquaza was particularly bad about this in ORAS, who thought it was a good idea to make it both mandatory to capture
and be sandwiched between two unskippable cutscenes, along with Deoxys being there more or less forcing you to just KO Deoxys to come back for it later if you want both of them to be viable. And event Legendaries are supposed to be gifts, I shouldn't have to be doing additional work to get a "good" one if I already drove to a Gamestop or whatever to go get it.
Let's consider how much of a pain Rayquaza was in particular for a moment. Groudon could be obtained later with a good Synchronizer, Latios/Latias was plot required and forced you to drag along a Synchronizer to a plot required fight with Team Aqua/Magma. It was a huge pain in the rear to put the plot on hold just to SR for Rayquaza and Latios/Latias. Now, let us consider that in SuMo, there are four Tapu Guardians, which we know for sure are obtainable, and the eight known Ultra Beasts all have shiny sprites, suggesting that they are also obtainable somehow. Then we have the cover Legendaries and Zygarde. Given what we know, Zygarde will be pretty plot-relevant as well. So, in total, we've got eight Ultra Beasts, four Guardians and Solgaleo/Lunala and Zygarde, all un-breedable and all presumably plot-required to capture. That's
fourteen plot-necessary Legendary/Mythical Pokemon. If there isn't some way to manipulate Natures in this game, soft resetting for each and every one of these things is going to be more than a chore, it will actively be detrimental to the game experience. Remember Rayquaza? It will be an
entire game of that, for every single boss fight. This, combined with the RBY connections, has me convinced that there must be some feature they haven't announced yet, or have made all Legendaries spawn with set Natures, because I can't believe they'd go through the trouble of removing HMs and streamlining IV breeding just to cram over a dozen Pokemon into the story that require us to waste ours soft resetting our games and/or dragging whatever equivalent to Ralts/Abra exists in Alola along to every single story encounter.
tl;dr fix the Nature system so we at least don't have to soft reset for Legendaries/Mythicals, because soft resetting is stupid.