Another PSA, this time about placements.
Seems like someone has to do this every year, but here we go.
Your previous MMR will very slightly influence your placements. If you were Silver 3, you're more likely to get teams who were also Silver 3. Due to the fact that MMR was mostly reset, queues are loose and you may get matched up into very hard teams.
Secondly, going 10-0 doesn't guarantee any rank. You could go 10-0 and get placed in Bronze III, if every team you beat had Bronze 5 MMR. Likewise, you could go 5-5 and get placed in Gold III if every team you beat had Plat-Diamond MMR and every team you lost to had high ELO MMR as well.
If you're really going to complain about getting Bronze when you think you deserve Platinum, sorry. Because even if you go 10-0 and get Bronze, if you actually deserve Plat, you'll have no problem climbing. You'll simply outskill your opponents, your MMR will skyrocket, and you'll be gaining 40 LP per win in no time. If you get placed in Bronze and can't climb out, then you obviously deserve Bronze and you just wanted to be placed higher so you could play very few games and turtle for ranked rewards.