Even before the changes in ratings, I can't say I found them that reliable. In some cases I think things have improved due to the changes. For example, the rating of The Fortress increased (it definitely deserved a higher rating) and most of the Japanese dramas in the high 7 range have stayed about the same, while the Korean and Chinese dramas in the 8s have dropped, so Japanese dramas don't seem quite as underrated as they used to. On the other hand, I don't think Six Flying Dragons deserves to be rated lower than a dozen no-substance rom coms, but ... whatever.
The point is that the new ratings aren't a great indicator of the relative quality of dramas, but I don't think the old ratings were either. The admins are trying to get rid of vote manipulation, so it should make the ratings more accurate to users' actual judgements. Since every user on this site has their own taste and uses their own scale and criteria to rate things, no matter what the admins do, it will probably always be a little out of whack and not always correlate to how good the shows actually are.
I find word-of-mouth to be more reliable than ratings. If people who know my taste recommend things, or if a show is generally acclaimed, that is probably more an indicator of how much I will enjoy it than the MDL rating is. I also agree with Parto0o, look at the synopsis, tags, actors, writers, directors, etc. I've only ever decided to watch one show due to it being rated highly on this site (that was before the rating changes, though it still has a high rating), and it has been a big disappointment to me.