This post does not "debunk" what I said. In fact, it explicitly mentions the Warburg effect as something to target as a treatment possibility. And looking at two of the molecular cancer biology texts I have to hand (I did a PhD which involved vascularisation, angiogenesis and HIF-1α/VEGF/EGF), there are several examples of drugs which target the pathways related to this effect directly.

Also note that the link does not say, at all, that dietary restriction of simple carbohydrates is ineffective. What it does say, is that dietary restriction should be discouraged in case it causes malnutrition and/or weight loss, which can be counterproductive with effective treatment which itself can also cause weight loss. Which are completely fair points to make for safe general advice to the public; nothing here is black and white, and making definitive statements one way or the other would be both impossible and irresponsible.

So in some situations it may well be counterproductive. However, that is not saying that there are no situations in which it can be effective. Cancers are incredibly diverse, each type evolving in a unique way with different courses of progression. In some cases, it may well be the case that such restrictions can help.