Of course!
My opinion stems mostly from talking with some comrades about the DKP. The only real experience with them is what I have read from their official program, I never met any of them personally.
In their party program they mostly just quote Marx and Lenin, which seems correct at first. However, this culminates in basic errors like proclaiming that we need to “strengthen the unions”, while it is a fact that most german workers unions are not working for the proletariat, or are even controlled by bourgeois-aligned socdems (at best).
So any principled communist would analyze the situation and come to the conclusion that we first need to reclaim our unions in the first place! Strengthening, or supporting them now would be idiotic. So that is just lazy at best and revisionist at worst.
This, through working with them in a united front, could be forgiven (on the condition that they, through combined action admit and learn from this).
But most comrades I’ve spoken to that met them (e.g.: were a member or worked with them in the past) told me they are mostly just old people that have gotten really dogmatic, lots of them turning to revisionism (hence me calling them Trozkyites, maybe a bit crude on my side).
KO (=Kommunistische Organisation) were mostly active online, though I’ve only once seen two people waving their flag at a local demonstration. Only seen some of their anti-China content. They have recently founded the KP (=Kommunistische Partei, duh), but it remains to be seen what they actually do.
Imo: Reactionaries always admire the barbarism that the rulers were capable of in feudal times and the trope of “everything will get better with the right leader in place” appeals to the idealism of liberals.