No mmr decay is unfair

Is it fair for someone who gets ranked high (masters/grandmasters/top 500) to be decayed only to diamond?

Think about it. People get put there. They dont play. Yes rank gets dropped but mmr stays the same. So when you play next season your mmr would place you in the same spot assuming you played the same or close to. Plus you get rewards on what you placed that season (season high) not actual rank.

Thoughts?