I find it kinda 'cringey' when people thinks certain archetypes have not strong enough. What a failure...
Most of all decks are more tan capable to reach KoG if you know how to play them. That's why there are Verified King of Games decks here and in Duel Links meta. King of Games Ojamas, Aromages, Six Samurais, Dark Magicians, JUNK DESTROYER... damn, plenty of different decks.
I think Six Samurai is kog material if you know how to play it. Shien can be summoned oput of the blue and you can start removing backrow with the archer
Some archetypes ARE genuinely not strong enough in DL, though.
Blackwings (thankfully), Madolche (needs their Xyz), Malicevorous and Umbral (their main use is as Xyz fodders, so without Xyz they're crap), Traptrix (still need some of their main deck cards, as well as their Xyz), are just a few examples.