Why do most Japanese dramas not achieve an 8+ rating?

Don't know if I'm right... 

Japanese Drama tend to have a lot of infidelity,cheating from the main characters which is something many users of mdl dislike,as well as that japanese drama for me have more raw realism than C-drama and K-drama and may usually come out as boring for that reason.

Also i think its evident that more people fangirl/fanboy over korean/chinese actors/actresses rather than japanese ones (not gonna lie japanese ML aren't the  super charismatic-good looking types beside a few where people would fangirl over) which infulence the dramas they watch.

Lastly i could be wrong but korean/chinese drama do have better productions (visually) which is important.Thats all my opinion though and what i could think within 10 minutes.

Edit:I also think  accessibility might be a reason as well,English subs from japanese drama are way harder to have access to than to Korean and Chinese drama and become available at a later time not the same day like the other two do so they do not get hyped up like the other two.Thats why if you look at Chinese/Korean drama while they are airing they have higher ratings than when they get completed cause the hype dies and they will likely get rated lower by 0.*% most of the time.

Because people in japan, apparently, prefer watching k-dramas and western series which leaves little demand for domestic productions. Lack of marketing for foreign audiences (evident in how most j-dramas don't even have offical subtitles for them) means also less recognition and less funding from foreign sources.

Thus, they are cheap, poorly acted and stagnating. Japanese aging population and work culture that doesn't favor innovation doesn't help, either.

Anime is good tho. 

Personally, I think the cultural differences are big part of the reason for J-doramas having a lower profile here. The anime/manga inspired shows really do have a very different vibe  to what many are used to, especially coming from a K or C Drama habit. The production values are often lower too, and that's a big turnoff for much of MDL's core demographic, I suspect. 

Bt to be fair ot J-content,  A LOT of MDl's ratings are driven by visual aesthetics of the actors, not the content of the shows. Shows get rated highly if their (almost always) MALE leads are considered visually attractive by large numbers of viewers.   The comments threads in the top-rating Dramas bear this out - in the end what wins a Drama 10,000  "10s" is the fanbase of its  male lead, not the quality of the acting or the brilliance of the writing or the artistry of the director, etc. There are fewer big name J actors with large fandoms here, so the 'pretty' factor is not in play. Add to that the fact that J-doramas often have very quirky content and are MUCH shorter than most K Dramas and all C Dramas, and  of the course the fact that many are either not subbed or have subs that are hard to dind, and the failure of J-doramas to gain high ratings at MDL is not surprising

Taste is utterly subjective of course, and there's nothing at all wrong with the fact that most MDL users don't care for J-doramas. The real problem is the exaggerated and unfounded importance many attach to MDL ratings. They mean NOTHING and say NOTHING about a show's merits, or lack thereof. My one wish is that people would stop fixating on MDL ratings as a guide to either the quality of a show or whether they personally would enjoy it, and sinply check Dramas out for themselves, wherever they come from. 

For me, J-doramas areeasily my favourite. My average score for Japan is 7.2, versus 6.46 for SK, and 20% of the J-doramas I've watched I've scored at 9 or higher, verus 11% for SK.  Personal taste should be one's guide, not the utterly meaningless MDL ratings