1) Comp is more important in 2s than any other bracket, and there are many comps(even played perfectly) that simply cannot win against others, so you end up losing to low rated players playing stronger comps.
2) Because of the number of people that queue 2s for points there are many more low mmr teams than higher mmr teams, so you constantly get queued into comparatively far more 1500ish mmr teams until you get past 1750 mmr yourself.
Makes it very difficult to get into the 1850+ mmr area in 2s, unless you 1) play one of the few strongest comps 2) get lucky with who you queue into until your safely past the cutoff where the queue system won't throw you in with so many 'points teams' 3) get queued against exploiters.
I had a 85% winrate 2s team that never got past 1800 because of getting thrown to the wolves in the queue system every 10-15 games against comps that were impossible for us being played by 1400 mmr points players. If the same happens to you, don't beat yourself up about it and just play 3s or 5s.
Only real advice is play a strong comp and try to play your best, and/or get lucky, for big winstreaks.