Raider IO isn’t a new thing. People forget we have had wowprogress all along, which also shows your experience in running dungeons and at what level. Raider IO has a better interface as far as how information is presented, but it’s not a new phenomenon.
What is new, however, is the awful culture Raider IO created. The people who, let’s say have a current best of a +11 Freehold and they get into a +12 Freehold, something goes wrong (e.g., group is totally capable of completing the dungeon, but may be a few minutes over time), then the person ends up leaving because it wouldn’t help their score. Now the key is dead and they’ve wasted the time of four other people. That is the problem. People running dungeons specifically for score, and pooping on the group if they don’t get what they want out of the run. Sadly, this happens way too often.
Raider IO Levels:
High level players (running +20 keystones) - not really affected since these groups usually run as regular teams. If you’re pugging these regularly you’ll either need to be known as a good player or you’ll have a hard time because it’s a small community.
Upper-mid level players (+15 to +19) - expect a lot of people applying to join the group to boost their score. Want proof? Look at applicants, notice their highest dungeon is likely one or two levels below the keystone you are listing. Don’t invite them.
Mid level (+10 to +14) - This is probably one of the worst brackets just because you will have a lot of people who paid gold to get their scores boosted (WoW is very pay to win these days) and you’ll never know who is a good player. People in this bracket will also leave if their score doesn’t improve, unless they’re just doing it for the weekly mythic cache (and sometimes those players aren’t very good either).
Low-level players (+9 and under) - Kind of dumb if they require a site like Raider IO for doing trivial content. Usually I’d just avoid those groups entirely since it’s like requiring a computer science degree to teach kids how to type.