"I was a higher rank last season, so I'm better than my lower rank this season"
No, you're not.
Skills fluctuate
Sometimes you're hot, sometimes you're not. Performance is not static, even for the most consistent of players. Outstanding players have slumps. Second stringers have good days. If you switch champions and/or roles, you're also going to perform differently. Haven't touched your old main in a while? You aren't going to be as proficient as you were.
The meta changes
Riot is constantly tweaking the game. Champions gain and lose power. Available items change. Players find new strategies. Surely you're familiar with the term "Flavor of the Month." The only reason it exists is because swarms of people learn about an effective approach that previously wasn't widely known or had fallen out of favor for a while. These shifts often cause changes in bans and force matchups that weren't as common before. If you're facing effective strategies that are unfamiliar to you, your performance will be hindered. Players who are familiar and comfortable with those strategies will flourish.
The playerbase evolves
League of Legends has been around since late 2009. That's roughly 5 1/2 years of availability to millions of people. That's a lot of time for a lot of people to play. So last season you were able to improve your gameplay and win ranked games consistently enough to climb out of Bronze into Silver. What makes you think that other people haven't also improved their skills? If you're on NA, you're one person out of hundreds of thousands in your tier. Odds are heavily stacked against you being the best one of them. You haven't played against them all. Even if you're Bronze 1 in your promotional series, there are many, many players ranked lower than you that are climbing faster.
Your MMR isn't a static value. Last year's 1100 (arbitrary number chosen for discussion) does not hold the same weight as today's 1100. An 1100 earned last year was achieved by playing against people who are most likely no longer roughly 1100. You might not even be able to beat those players again, since they could have improved more than you have in that time. New players at the 1100 mark might be better than last year's players at that mark. Other than seasonal placement modification, your MMR from last year is completely irrelevant. You are placed in games with average MMRs similar to your own. Your MMR is adjusted depending on how consistently you perform against other MMRs. Keep winning against higher MMRs? Your MMR will increase. Lose against lower MMRs? Your MMR will decrease.
While last year you may have reached that higher tier, there are many other players who have also reached your MMR that you have failed to beat. There are also players who were higher than you that have dropped to your MMR, so you are competing against other "fallen" who are probably still better than you. You could also have been placed too high since the MMR system needs you to play over 100 games to tighten its margin of error.
You are your current rank
If you were Silver last year, but Bronze this year, then you are Bronze. If you can't climb back out of Bronze, then obviously you shouldn't be Silver. If someone was Diamond last year and somehow dropped into Silver without being able to get back out, nobody would consider him Diamond. He'd be called out for being an intentional feeder or a boosted/sold account.
Given the following, what do you think a player's rank should be?
- Player wins 100% of the time against full Bronze/Unranked teams
- Player loses 100% of the time against teams with Silver+ members
Some would say he should be at the bottom of Silver. Others would say he should be at the top of Bronze. People who understand MMR would say it doesn't matter, because there is almost no difference. There are Bronze players with higher MMR than Silver players. Division V players are very similar to the Division I players of the previous tier. The primary difference is that the upper tier players managed to pass their promotional series.
If you think you should be a specific rank, prove it. Be that rank. If you can't, then you are wrong. Stop rationalizing that you are better because you once reached a higher rank. When you complain about being stuck lower than your "real" rank, you come across as a whiner that is never going to improve. A one-time rank below Challenger (the exception since you can be demoted without losing) doesn't prove that you are that good unless you can maintain it. Stop calling everyone around your rank trash, because if they're all trash and you can't progress past them, that doesn't say much for your own skill.
This message has been brought to you by unranked trash. Don't let that bias you, though. Last season? I was unranked. *touts past performance*