My Rating Scale:
The Good: Give Me More
5: One of my favorite series or seasons of anime ever -- I've only given out maybe 15 of these, and I gush when they come up in conversation.
4.5: Awesome, top-tier, best-in-season anime that I actively push others to watch.
4.0: Beautiful, consistently engaging, far above average anime. Beyond just being entertainment, this is one of the best anime of its type. There's a lot to like here, and I'd happily discuss it in detail.
3.5: Solidly entertaining anime that stick out a little above the pile when you're thinking of that particular genre of anime. Nothing to write home about, but they're good if you're into anime. I'd watch more of this without hesitation if it gets sequels or more seasons.
The Meh: Don't Need More
3.0: Decent but definitely flawed. Weird plot points or characters that didn't really come into their own. Overall aight, but I probably don't have much drive to watch it again or recommend it to others unless a later season is better. The type of show that makes me think "That was alright, but man I watch too much anime." (I see a lot of 3s.) If it gets another season, I may watch it, but it didn't do enough to stand out for me to be excited about it.
2.5: Disappointingly boring...I probably waited for something to change and nothing did. Empty calories: not especially terrible, but not good. It didn't have much to say, and it's not worth the time. Possibly especially heavy on tropes, the characters didn't hook me, or the plot fell apart or is just blah the whole time. But regardless of why, I didn't enjoy it much and wouldn't watch it again. 2.5 is the mark where I'm doubtful about watching more seasons.
2.0: This earned active eye rolls from me multiple times. If this is the start of something and it gets more seasons, I'm out, period.
The Ugly: No More, Please
1.5: I probably hate-watched this. For me to give something a score below a 2 means something was REALLY off. Maybe I disliked even the main character, their goals didn't resonate, or I don't even understand how their world works. Maybe I think the main character is a pretentious jerk and am annoyed that the rest of their world doesn't treat them as such...but I'm actively hostile about something in this show.
1.0: "Worst of its type" shows with glaring flaws so bad that it can be used as exhibit #1 of its genre gone wrong. This doesn't mean everything is bad, but there are unignorable bad parts that are ruining it for me.
0.5: I couldn't find anything redeeming about this trainwreck. It actively makes no sense, undermines its own mood-setting, doesn't develop its characters and villains well, and was a total waste of time from beginning to end. I only score things I finished, so that means I had some reason to think it'd improve...which probably means this is a terrible adaptation of something I actually liked in its previous format. Currently I've only given this to "The God of High School" anime.