Yes. I trust the ratings on MDL, more than on other sites actually. But I adjust them in my mind. I did roughly the same observations as you.
If it's a korean drama, I deduce 1 point.
If it's a thai drama, I add 1 while thinking I might still fastforward some screaming and side characters scenes.
If it's an old drama, I consider it will be quite good as long as it's above 7.
Also, I avoid sad endings unless it's an ongoing drama but this usually downgrade the ratings by 1 or 2 points.
The ongoing dramas ratings reflect the quality of current episodes, it only gives a hint.
I don't trust completed or dropped ratings. The ones who completed it mainly liked it, the ones who dropped it mainly didn't like it so it's biased. Still, I find those numbers interesting.
Verified/Stars ratings: we don't know what are the criterias to be a star member so it's difficult to trust them. But it's true this is often close to my own ratings, so I do check them.