I must not understand what a reset is then. I figured we all start back at zero, like at the beginning of ranked seasons, then you place and go on with your ranked play. Why would everyone just be thrown back a full rank?
In games not called Overwatch, resets are usually "soft resets". You never gain ranking after a soft reset, even after promos.
So lets use League of Legends which IMO does it mostly the right way...
Take your current MMR (which they hide from you), but lets say it's 2500
1200 is their net 0 rank, like if you went exactly 50/50 win/loss you'd be 1200... it comes from the old ELO system.
The reset formula is (CurrentMMR+1200)/2
So (2500+1200)/2 = 1,850.
1,850 is around plat IV in LoL.
2,500 is like Diamond I.
So 1,850 is the reset MMR and THEN you have promos which are +/- about 50 MMR a game, which is about 5x more than usual. If you win all 10 games that's +500 MMR to sit you around 2,350, however, League caps you out at Plat I, so even after Promos you will be finally placed at Plat I even though your hidden MMR is like Diamond III tier.
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So even at best case scenario and winning all 10 promo games, you still lost several "tiers" of hidden MMR, and quite a substantial tier of visible ranking since you went from Diamond I to Plat I. But the good players will rank back up the hard way and bad players will face the struggle again.
Conclusion: You never gain ranks, and quite often you will lose many ranks. Like go from Gold to Bronze and shit.
edit: and if you're still confused, what Im saying is the very best OW players would de-rank to Plat, and the plat players would de-rank to silver/low gold, and the gold players would de-rank to bronze/low silver, etc.
edit2: Correction, the very worst players do GAIN rank actually, as they come closer to the 1200 spot even though their rating might be sub 1k