For me, a 5/10 is "poor", 6/10 is "alright", 7/10 is "good", 8/10 is "great", 9/10 is "fantastic", and "10/10" would be perfect. And with my 75% subjective/25% objective rule, if you thought something was truly objectively trash but you love it anyways, 7 to maybe 7.5 is about the highest that I'd ever give it. From the sounds of it, you don't think it's particularly close to trash, but you also didn't quite love it, so maybe 7/10 is just about right. I give out 6-7/10s pretty easily - as long as I mostly enjoyed it and it wasn't actually badly made, it's not too difficult to get that 6 or 7. 8 and above is what's difficult, because an 8 is supposed to be "great", and what is "great" does not come around very often in my eyes.
I think I've said this before, but when I watch RLM videos about movies/shows, I evaluate not just whether they liked it, but what they actually say about it. They may call something fantastic, one of their all-time favorites, one of the best things they've seen in years, etc., but I may very well know right off the bat from what they actually say about it that it doesn't appeal to me at all and there's almost zero chance of me enjoying it, so I don't care about it at all, and just watch their video for entertainment. On the other hand, they may say they simply liked something and get just a few sentences into actually talking about it before I close the video because I already know I want to watch it before they really go in-depth into it, and I'll watch the rest of the video after I've seen it. In a way, the same kind of process applies to your posts when you talk about a show like Nanoha - it's not just whether you or somebody else likes it (even if I implicitly trust the judgement of the person talking about it!), the specific things mentioned about it are what actually informs me whether I think I'd enjoy or hate it.
It's a style and artistry thing. Miyu is a bit dark and definitely tragic, but it isn't really over-dramatic in your typical ANIME DRAMA fashion. The show isn't constantly trying to hammer into me the idea that Miyu's circumstances sure are the Big Sad, or that she's this totally normal and relatable character, or heck, that we should even necessarily be rooting for her at all times. Miyu was a show where one moment, she expressed concern because she heard a woman's scream far off in the distance, and literally the next moment she smiled and basically said "all is right with the world" because her fears were apparently assuaged when she then saw a dude jump off like a fourth floor balcony to his death. It was a show where I initially strongly disliked one of the secondary "protagonists" in Reiha, that I actually then started to like when she instead became a primary antagonist because I, like her, started to question Miyu and her methods and what she had been taught and thought that hey, maybe Reiha actually has a point here (even if I don't necessarily agree with her entire outlook either) and also, what she has personally had to deal with has kind of been a rough deal as well. It's a dark but soft and grounded anti-magical girl show at its core, with some unusual interfacing of smaller, nicer character moments and dark ideas and themes. It wasn't a perfect show by any means, but it's the only one of its type and it worked for me.
But most importantly (), it's a show where the promotional posters look more like...
...instead of...
The style, the artistry, the intended tone, the appeal, the...everything is, uh, a little different, to say the least. As always, I'm a big believer in shows/movies being what they're selling themselves in at least tone, style, and intended audience, and Miyu literally immediately interested me based off of what it was selling itself as soon as I saw it and and it held up its end of the bargain, and Nanoha...would likely do the same, except in the exact opposite way since very little about it, except for the good things you've had to say about its general writing quality, is even kind of appealing to me. Between...
1. The mentioned fan service...
2. Too much action...
3. Over-dramatic action...
4. Lack of (or way too "big" i.e. not grounded, not relatable, not interesting, or not even funny) character stuff...
5. "Epic" story stuff... (note: this is what I love about Miyu and Sakura over e.g. Sailor Moon - grounded and low-key stories that are incredibly personal to our characters instead of generic END OF THE WORLD-type nonsense that I usually just want to get over with as soon as humanly possible...if you want an epic, world-ending plot, you're going to have to really build up to it and get me into it a la Steven Universe...which of course, had its own problems in the ultimate execution of it, but at least still did a good job of getting there over the course of many seasons)
6. The general aesthetic...and holy crap, kill these character designs with fire, ye gods it's so incredibly bad - I know even newer anime gets so much worse than this, but man...
7. idk probably other things
I just don't see it working out in any way for me. I like things to be done in a particular way, I want things to look a certain way that fit the tone and (non-visual) style of the show, certain styles of voice direction make my skin crawl, I want all the elements of a show to marry each other and form their own specific and cohesive style, and I just...you know, as always, I'm very particular. And I've always said that I experience what I hate much more strongly than what I like, so if even one element is misused or out of place in a major way, or something does the complete opposite of appealing to me (especially something fundamental that you would notice in a new show right off the bat that's going to be constantly there!), the entire house of cards collapses before it's even been built and there's virtually no hope for me to like it. Now, the chances of a show having such incredibly terrible music that I immediately hate the show in question are pretty low, especially because music tastes are malleable to a degree and different styles are appropriate for different shows...pointless and inappropriate nudity and/or fan service that involves the main characters that I'm supposed to like and take seriously, on the other hand? Yeah, that could do it, .