The population for season 3 vs season 9 is large enough in both cases that they do not have any statistical significance for the ranked distribution.
If the population of the ranked players in season 3 was 10 players then you are correct.

1) If OP is asking how a season 3 1500 ELO player would perform in season 9 then it would be FAR from platinum 2. It would be closer to bronze probably.
2) If OP is asking if we used old ranked distribution on today's players how would a 1500 ELO player in the old system look like today? It would be platinum 2.

You learning curve argument has nothing to do with point 2.

Point 1 is subjective.
Point 2 is objective. It is how it is. UNLESS the sample size of either population was too small to have any statistical significance.

As much as I'd love to participate in an intellectual debate, I unfortunately don't have the time to source sufficient data today. Perhaps I can respond with more statistical evidence later this week.

1. There IS a significant statistical disparity of ranked players between season 3 and season 9. You're probably seeing statistics about ACTIVE players, rather than AGGREGATE players. Note: if a player plays ~8 ranked games over the course of 11 months, they are included in the statistical distribution of ranked players (although important to note, they wouldn't hit the bar of daily/monthly "active player"). Even if S3 and S9 don't differ significantly in ACTIVE ranked players, there is significant disparity in AGGREGATE ranked players (which therefore impacts % placement). I'm sure I can prove this to you if I spend 30 minutes to gather sufficient statistical evidence - which I'd probably be willing to do later this week depending on this conversation.

2. It's difficult to assume what OP is asking given the phrasing of his question, "what would you say S1-2 player is today?" - but my interpretation is that it is closer to #1 in your post. Yes, it is subjective, which is why it's important to take into consideration my two aforementioned points.

3. I don't think your "statistical interpretation" of platinum 2 is scientifically accurate, nor is it completely objective.

Side note, curious what rank you are?

This post was edited by MidWinter on Nov 17 2019 07:06pm

not everyone asks that, pointless anyway, makes like no diff

ive done hundreds of boosts. never seen one get banned

This post was edited by bigbadwolfhuffandpuff on Nov 17 2019 07:06pm

happy to take this discussion offline (into PMs and off OP's thread), but it does matter if you're not able to boost even yourself to diamond without using two champions.

btw, the "less obvious" part is not about being banned or being less obvious to Riot. Not everyone likes to publicize to their friends that they are being boosted.

This post was edited by MidWinter on Nov 17 2019 07:08pm

lol I can if I want man. just playing random games with random champs at end of season in every role

ill boost to diamond every role for 30k fg ill bet 30k fgs on it

This post was edited by bigbadwolfhuffandpuff on Nov 17 2019 07:08pm

So I'm understanding correctly - you never climbed beyond D4, and then decided to intentionally derank yourself 1 week before season end?

You don't have 30K fg to bet. But sure, I'd be willing to make some kind of fg bet on that - boosting multiple fresh/low MMR accounts to diamond, playing solo, on each role.

I am quite sure 8 games wouldn't be enough since they wouldn't be placed. But I get your point I didn't account for that. However, same argument could be made for current season players. It would actually be nice to present the methodology and see what the actual distribution would be.
Unfortunately don't have enough time until next month, if you find season 3 data let me know it would be cool to calculate. I don't think it is possible, since I am quite sure Riot's API only started to show this to the public season 4 and onward.

I have only played my placement this season. I haven't had too much time to play. Won 8 of them and lost 2 and placed Platinum 1 with 94 LP. Realistically I am minimum a diamond 3 player.

8 games is the amount of games required to place this season in soloq
https://na.leagueoflegends.com/en/news/game-updates/competitive/whats-new-ranked-2019

This post was edited by MidWinter on Nov 17 2019 07:27pm

I see haven't played seriously since April so I am bit out of loop, what is your rank?

Former masters, been hovering D2-Masters depending on # of games played for every season since S4.

Made 50k+ FG from boosting on jsp for the last 5 years (see prof)