They are very important in order to
- Fuck with boosted people
- Shake up higher elos so people can practice with players who are on the higher level than them
- Punish inconsistent players
- Put things back into order after the offseason (not having ranked in the offseason is important because that's when most of the large-scale changes happen, and riot doesn't want that to be abused in ranked in any way)
If you got placed into bronze 5, that's very sad, but if you know for a fact that you're better than that level, you should be able to climb out from there.
Also, you ended at bronze in season six. Did you really expect to end up at a good level?