How Exactly Does Normal MMR Work?

Hey,

so basically i've been leveling up a new account with friends just for fun. Currently at 90% WR in 60 games but we are still only facing smtn about mid-high dia players. The issue here is though, that we are literally waiting 20+mins for each games which is really annoying because the games alot of the time dont even take 20mins. Is League really dead or is our normal MMR just too high? Thanks in advance