I actually agree with you in the fact that, "because it's vanilla", isn't a good excuse to not fix shitty Mojang janks. I've argued way too long that powered elytra are way too overpowered, but have always been countered with bullshit like "But it's vanilla", or "Just don't use it then".
In terms of phantoms, they are very anti-fun when you are building outdoors. You cannot decisively counter them all without being hit, killed, or knocked off your building, without 'sleeping' in a bed that may or may not be far away. If able, I think they need a soft nerf, maybe something you suggested, maybe something else, I don't know for sure.