Saying that the plot wasn't convulted, or wasted is having never read this manga, or any other literary medium.
The fights lost what made them good, and became confusing, first trowing the Furyuku, Reirokou, and Whateveroukou numbers around, later power tiers, then feats of impossible strenght, and finaly asspulls of random skills.
I used to love this series, but the author didn't cared as much as I did, what are the conditions for getting forced to end a manga? how many weeks in the bottom of the questionaries?
Takei didn't understood the meaning of a good battle, even if the basis were there, they almost always (after america) had a big flaw.
And the techinques… how many times did Lyserg used the Phantasm Big Ben?, or Yoh the Budah Giri (after america)? Did Ryu had any named tecnique with susano cleaver?, did any of the Gandara (sans reviving sati) had any particular skill apart from "Furyuku Nullification in form of <insert used="" budist="" weapon="" here="">"?
And don't get me started in wasted battles, Sati and Jeane getting killed off screen by hao's henchmen, Anna losing against Hao offscreen, the battle of Sati vs Enma, offscreen, Hao's first and second death, the second set perfectly to happen when Yohken apareared, the Hell training (the inner demon manifested battle) skipped, the final battle between Marco and Luchist offscreen (eh, that one I'd rather to be keept offscreen, the pedophilic tones were too much).
Too many details, just in the biggest shounen aspects, the finner plot points would be too much effort.
Even though, an ending is an ending, finaly.</insert>