This is sort of a response to all of your posts on this, not this specific one, but here's a summary:
-Since Pokemon didn't previously appear in the overworld, you had to actually do into battle (or hatch an egg) to see a Pokemon at all.
-Some games - I believe specifically the 3DS ones? - introduced weirdly specific methods of raising the shiny encounter rate that would give some indication of a shiny from the overworld, but generally speaking you were already shiny hunting if you were seeing this.
-Upon entering battle with a shiny, there'd be a little animation/noise. Other than the palette difference, this was your only indication most of the time.
Part of the problem is that the system was originally designed with random encounters in mind. Now that we have overworld Pokemon on the Switch, the rules have changed, and Game Freak has yet to decide on a system.
-Let's Go showed shiny Pokemon with sparkles.
-Sword and Shield gave no indication prior to entering battle.
-Legends: Arceus returned to showing them in the overworld (pretty much necessarily, due to the lack of camera cuts when entering a battle and the fact that battling is optional entirely) with sparkles and a sound effect. I'm not sure if Let's Go had the sound, but it's very important in Arceus due to the free camera (as the sparkle can occur off-screen).
And now they seem settled on keeping them in the overworld but removed the obvious indicator. Presumably, this back and forth has been due to the change overworld Pokemon have in the perceived rarity of shinies. You're effectively churning through way more encounters than in the pre-Switch days - and thus more likely to run into a shiny on sheer volume - and Game Freak appears to be trying to balance that without changing the shiny encounter rate directly. Anecdotally I'm seeing a crazy number of shiny Pokemon caught from these games, despite the fact that the rate is the same 1/4096 it's been since gen 6.
As for your suggestion on identifying them being part of the fun, I agree - but due to the way the Pokedex works, I understand why everyone wouldn't be happy about having to spot a subtle difference themselves when there's not even a reference to look at until after you've battled the shiny variant at least once.
There's also an accessibility component here. I wouldn't be shocked if a colorblind person who can't easily the difference between regular and shiny - say, Pikachu - would still want a shiny one.