Changed my rating structure
0.5-2.5 = Terrible to Below Average
3-3.5 = Decent to Quite Good
4-4.5 = Great to Exceptional
5 = Masterpiece
I judge anime in two main ways.
Firstly, from a technical perspective, judging the animation, OST, voice acting, characters, plot and etc, was it done well.
Secondly, how enjoyable or good each episode was overall and/or how good the buildup and conclusion was.
Some anime possess impressive features but the majority of episodes were uninteresting. I'd rather watch something slightly worse where every episode is fun and interesting or if the buildup and payoff for the story is striking, that's also important. Obviously, there's personal bias with preferences. I do try to judge an anime for what it is. I don't expect a comedy to have the greatest OST or animation, if it was very funny and entertaining then I give it a high rating, etc.
I don't expect many ratings less than 2 because I don't rate anime that I drop and I usually don't finish anime if I realise it's bad early on.
For many anime, I watched them many years before changing my rating system, if I don't remember well enough how it went or what I thought, I do not provide a rating and thus, I left many anime unrated because I don't remember them well enough.