This is really only true of the shows from Faiz through about Kiva, where production was rushed and shows clearly began production with no planned ending (or changed plans for the ending halfway through). Kuuga, Agito, and (it appears) Decade are all actually quite consistent in terms of writing, moving clearly and consistently toward an obviously pre-planned ending. Kuuga, in fact, means basically nothing without its ending.
Ryuuki is poorly written in a different way. Basically, the show doesn’t have one resolution. It has 3-4 different ones that apply to different tellings of the story. There’s a TV ending, a movie ending, and a TV special with I think two different endings. Each of the endings offer different “answers” for what the Rider Fight really meant and what was really motivating key characters.
As a result, individual Ryuuki episodes watch decently but the show clearly just doesn’t mean anything if you look at it as a whole. It was an excuse for kewl people to wicked-awesome armor to punch on each other while CGI power animals waggled around the screen. Characters will do things that make no sense in the long run and many mysteries are never addressed despite the many endings.
For some fans this is not a problem, especially if they like the more modern style of Rider as a delivery vector for colorful fights. Some people also like the openness of basically being able to decide for themselves what was important about the show and what the Rider Fight really meant. It’s not typical of the franchise, though, and not for everybody.
I’m surprised by your comment about MKV, though. It’s almost the only format I come across when downloading new fansubs (other than the ever popular Naruto/Bleach). I actually thought that MKV is loved only by anime and blu-ray rips.
There are particular groups that are very fond of MKV, especially the Blu-Ray rippers. The vast majority of fansub releases are still provided primarily in AVI and MP4 formats, though, and it’s not hard to stir up a nest of MKV-haters on anime forums.
MKV’s main issue is that it’s not very portable and a sizable portion of the American fanbase dislikes watching on their PCs. MP4s convert easily to Apple portable devices and AVIs convert easily to PSP and can be played by DivX DVD players. To my knowledge, you can’t run MKVs on anything that’s not a computer and they have issues outputting to VHS (yes, some people in the US still do that).
To this day there are “re-encoding” that do nothing but strip extraneous things like multiple sub streams out of MKVs and then redistribute the subs in a hardsubbed AVI format with reduced video quality. A lot of people prefer these files to the original MKV files because they can be downloaded more quickly!