I only use MAL for lists now, so I'm not currently accepting friend requests, am not likely to reply to PMs, and comments are disabled. If you need to contact me, leave a comment at someanithing.com.
• I rarely rate shows I don't finish, unless I've seen at least 6-7 episodes.
• I rarely finish shows I don't like at about a 5/10 level. Life is too short to watch anime you don't enjoy. Better to drop and dedicate more time to what you like.
• I infrequently rate specials and OVAs.
• And I don't believe that 10/10 has to be reserved for "perfection". It's 10% of your available options, and therefore there's no reason why it can't represent upwards of 10% of franchises. I do try to keep it down closer to 4-8% myself, depending on whether I include dropped shows in the denominator.
Therefore, the vast majority of what I rate, especially if it aired in the last few years, is going to have a 5, 6, 7, 8, 9, or 10. There are plenty of shows down at 5 that I actually enjoyed a fair bit at the time. But my approach is to periodically (at least a few times a year) revisit the whole list with the intent of knocking down by a point as many titles as I can if looking at their title doesn't immediately bring to mind specific things I really enjoyed. Over time, only the shows that actively retain my favor long after they've ended will stay ranking high. The shows that just happened, entertained me, and then went away will eventually find themselves down at 5. Changes in my tastes will of course get shows lowered too.
But tl;dr, 5 doesn't mean bad, it means I feel no lingering attachment to the series.
4 is generally reserved for very flawed shows that actively bothered me in some way, without significant upsides to make up for it. 3 or below is for truly terrible shows. More often than not, I've dropped and not rated shows I really dislike this much.
10 is reserved for the best of the best. These days only 1, maybe 2 shows a year get a 10/10.