To be fair I think the raid system is quite balanced. You have to put effort into your account though to be able to raid with less people.
To put it in perspective, I can do a Raikou, Entei, and Suicune raid with 4-5 people. I can do a Tyrannitar, Golem, or Rhydon raid with 3 people. I can solo most 3 star raids myself. I am level 37.
If you failed a Tyrannitar raid with 8 people that just means most trainer levels were too low and/or you didn't have strong type match ups (e.g. fighting).
Just work on identifying which raids you want to work towards and look up which Pokemon are strong against the raid boss. Get proper move sets, increase your trainer level and power up your Pokemon. Look for raid bosses with double weaknesses (e.g. Tyrannitar is Dark/Rock which are both weak to Fighting, Golem and Rhydon are Rock/Ground which are both weak to Water/Grass). The raids may be tough now, but they do get easier over time.