A good point, but I hated T.K. and Cody so much, Shakkoumon was literally the best Digimon to represent them because he was laughable. He still got a decent boost, being able to resist BlackWargreymons attacks several times before he (still) managed to find a way to destroy the destiny stones. I know what you're saying, but I still don't think it was worse than Frontier.
SkullSatamon shouldn't have even had such a huge effect anyway. He's just an ultimate. Just the writers way to show some adversity and present the Fighter Mode.
You know what's funny about that? Cody's Armadillomon would have evolved into a Shakkoumon anyway, without T.K.s involvement, ditto for Yolei and Silphymon, and Davis and Paildramon. The whole DNA digivolving thing was just tedious, and the partnerships didn't make any sense. It would have been better if they just stuck to armor evolutions, since they could switch around their armor (armor evolution doesn't require the characters to have the trait they represent just compatible digimon).
In terms of quality for me the seasons rank as
Tamers> Savers>Adventure>X-Evolution>>>>>>>>>>>Adventure02>>>>>>>Frontier
I haven't finished with Xros Wars yet so I didn't add it.
Tamers is pretty awesome cause it ages well, and can be easily watched albeit appreciated more when you watch it when you're older.
Savers was just fun
Adventure started it all
X-Evolution was a good movie, would have been better as a full length series though
Adventure 02's only redeeming factor was Ken, and the story with Oikawa minus Arukenimon, Mummymon, Myotismon, and Black Wargreymon. Otherwise it was horrid, and no watching in japanese doesn't help. Plot holes galore unlikable new characters and shafting of the older more likable characters, lack of wonder with the digital, lack of any real sense of danger, lack of common sense in story telling, and no central planning
Frontier was a season whose concept was okay but its execution left much to be desired. Unlikable characters, horrid storytelling, which just got boring and tedious at times, and a Spotlight Stealing Squad, seriously the legendary warriors are an awesome digimon group and yet we don't get to see most of them. Which is disappointing for a series centering around them.