Diamond rank is way too easy to get.

[Zojha]

[...] which is not how they should work rankings.

If they did rankings right, you'd need a 51+% winrate to climb and would fall at 49-%. There would be no minimum rank protection, no systematical disparity between rating gained and lost and no promotion matches - You're in if you got the rating, you're out if you lose it. And matchmaking would be done by searching for people of your rating +-50, not look across tiers.

That's what ranked would look like if they were serious about it. They aren't. Ranked is a joke played on people who miss the punchline in their fervent desire to take it serious.