2009 player here to help give you the perspective of someone from the extremely wealthy side of things. This is not an ego trip, I'm just hoping it might clarify some issues.
First of all, I agree with Mati on most of what he said. You can't just go "screw the old players!" because a bunch of people are sad at the situation. Keep in mind new players are coming to a game that is a LOT more stable. I lost 2.4 billion pure pokedollars back in 2010 or so. Old players have more stuff, yes, but don't be so harsh as to forget that we had to deal with the same crap, but worse, and for a longer period of time. Just as an example, shinies used to have a 20% boost compared to nonshinies. This meant pokemon got DOUBLE the stats natures give, JUST BY BEING SHINY. The only reason nonshinies could even compete then was due to the nature of having no switching then. You could just place a counter.
I'm not saying people aren't entitled to their opinion, but I'm saying keep things in perspective. You aren't dealing with robots with no experience here.
Another thing to keep in mind honestly. The difference between old and new shinies in terms of damage calculation is less than 2% in most cases. Most times it ever goes higher is when you are dealing with super effective damage on lower base stat pokemon. IE: physical dark hit vs something like alakazam. Old iv shinies, compared to new, AREN'T that broken. The random fluctuations in damage outputs created within the game's system has more variation than the difference between 20 and 28 iv. This is objective math. Go to the smogon damage calc and check it yourself.
The only stat that functions differently is speed. Every point matters for that. Now for stuff like 32 ivs in this, it has more of an effect. I'll address that below. Keep in mind however that the difference in speed ONLY MATTERS, when vs something of the same speed tier, nature (when implemented), AND same EV spread. Most of these situations however are NOT ADVISABLE to stay in, and SOMEONE will switch. Example: Metagross vs Cloyster. Who in their right mind would allow a cloyster to take a meteor mash from a metagross, especially shell smash variants? No one smart. They would swap into something to deal with the metagross better. (I'm looking at you weezing/slowbro/bulky starmie/etc.)
I hate to say it but most of this "old iv shinies are OP!" stuff is on paper, not in actual combat. Do I min-max the stuff I own? Oh yes I do, because I can afford it as a player. The majority of my time on PWO I used epics and common shinies. Back in the day I used tropius to counter bulky waters since i didn't have a good jolteon or a shiny exeggutor. On the flipside however, I used a shiny togekiss with 9 defense ivs for MONTHS. Why? Because it STILL WORKED. Player skill determines the majority of what happens in a battle, not ivs. 8 ivs between old and new is not what determines a match the majority of the time. It is not what determines a KO or not most of the time. A bad switch, or a bad prediction does far more to hurt you than those 8 ivs. The argument should not be, does it EVER effect things, but the complaint seems to come from an understanding that it is a deciding factor OFTEN. This is objectively false due to the nature of how the game is programmed.
Even still, the pokemon that HAVE 32 speed, aren't problem pokemon by and large as far as shinies go.
No 32 speed variants exist for the below OLD shinies (and more, but I am only listing metagame relevant pokemon off the top of my head):
gengar / starmie / tyranitar / salamence /dragonite /metagross / jolteon / weavile / scizor / mamoswine / arcanine / alakazam / espeon / heracross / honchkrow / starters / etc.
No max speed variants exist for the below OLD shinies (again, more but blah blah off top of head):
tyranitar (only one is banned), salamence (never existed), dragonite (never existed), Weavile (There might be one somewhere but inactive as far as im aware), heracross (only one banned), Starters
Notice how the higher a rarity goes you don't even get max speeds anymore? (Some of them only 1 exist and inactive.) Some of those pokemon NEED max speed. So the ironic part is running an old iv shiny salamence actually hinders you in some situations, while helping in others. It isn't just a one way street. Choice scarf tyranitar needs max speed to outrun a max speed starmie to thunder punch it in the mouth before you get scalded.
More on 32 speed:
32 speed pokemon hardly exist, mostly inactive. The ones who even have 32 speed only have extreme instances where it is relevant. Kingdra for instance has the same base speed as heracross, and nothing else really hits that speed. It only matters in kingdra vs kingdra or kingdra vs heracross. Heracross is scarfed 80% of the time so doesn't matter. Kingdra vs kingdra, the speed only matters if you both lead with it and try to duke it out.
Gyarados, base speed 81, ties nothing else relevant for speed. It only matters in gyarados vs gyarados matchups, again only mattering if you lead with it and have same ev spreads. Bulky gyarados is a thing, so you might not even need to rely on the speed for that if you run 252 in yours.
Only 1 crobat exists that I'm aware of and it's inactive.
You get the point.
It isn't as one sided as people think it is. There isn't even an old iv shiny for every pokemon that has been in the game for ages. Not to mention that in most cases when a person has a really rare shiny, they don't have tons of other stuff too. Let's also remember that most of the people with these things are collectors who have NO IDEA how to battle properly. I could name off a handful of people right now that haven't even EV trained their expensive shinies but I don't wish to point fingers in what could seem to be a malicious manner. (If you are one of those people, please do not take offense. I was just saying you aren't active in the battling community to even be one of the ones complained about.)
So we have an objective collective case of the following:
1. Old iv is not obscenely stronger than new iv.
2.It is really hard to find someone who meets the criteria of 1. informed battler, 2. arsenal of old METAGAME RELEVANT shinies 3. actively uses them vs new players.
3. Given 1 and 2, it is really hard to make the argument that old players win because of ivs on a large scale.
So the question becomes, why should people who have been loyal to the game be screwed because of PERCEPTION, and not reality?
28 iv sp atk with 252 ev investment gengar focus blast vs 252hp/252spdef umbreon
20 iv sp atk with 252 ev investment gengar focus blast vs 252hp/252spdef umbreon
So what we have here is 4.7% chance to 2hko changed to 1.2%. This is marginal at best. Stealth rock and leftovers recovery effect the math more than that. The swing of damage in the possible damage outputs section is 8% roughly. That is 8x more than the difference in damage because of ivs, and roughly 2.5x the difference between the 2hko chance change percentage.
I know most of you won't actually care. I know most of you "feel" you are right. I'm not here to argue with emotions and perception. I am here to deal with facts, objective facts. If a tree falls in the woods and you didn't know about it, it still fell in the woods.
tl;dr
Old ivs arent why people lose, skill and knowledge in team composition and execution are.
A lot of the old and rare shinies are in the hands of inactive players or non-battlers that dont effect you anyway.
mathmathmathmathmath did i mention math?
Disclaimer: The "this doesn't exist" section is not objective nor intended to be. This is just coming from years of being in trade and guild xats and seeing things pass hands. There is always the possibility that one random guy who never talks to anyone or posts anything has something no one knows about. However for the purpose of the above, that person isn't part of the problem causing people distress over old ivs in battle.