1. Not even Trying, would want to boot: No Job Stone, No Stance Tank, Blizzard 1 spam BLM, people who constantly AFK and aren't even moving. People that use shared gear levels 1-60 with the wrong stats. I don't run into these types very often but when I do, they are memorable and infuriating.
2. Underperforming: Bards that won't use songs, Dancers who won't dance, AST that won't use cards, Tanks that don't mitigate, Healers who only spam their single target DPS skill as teammates die around them, Healers that do nothing but wait for something to heal which means they have long periods of time idle, in fact any player with long periods of not casting or doing anything. I run into these types more than I'd like but still overall it's not super common.
Newer / learning players also often underperform but I expect this and it doesn't bother me. Also severely undergeared people who are at least trying.
3. Basic Competency: You generally use your toolkit at appropriate times and engage with your job's core mechanics. You're gear is at level or only one tier behind content. A majority players fall into here in PUGS.
4. Overperforming: You are over-geared for the content and also know how to play your class optimally.