It depends on one's patience and willingness to dive into such a big story. Maybe people (like Adam Roberts?), who normally rather read short series, stand-alone novels or short-stories are simply overwhelmed by the many details, plot-lines, foreshadowings, characters, factions, riddles, etc., in the WoT. They call for resolutions even already in the middle of the series, because they can't see what the point of such a detailed story is (especially if they already seem biased against the books from the start). That Roberts apparently thinks that EotW is a better book than TSR or TFoH, is in my view completely incomprehensible. Maybe the special but intentional format of these "monster-fantasy series" simply doesn't work for such people with a shorter attention span. Likely Roberts also couldn't bear to see six seasons of Lost to get to the resolution, but already skip the series after the second or third season, because (naturally, though!) few things are resolved till then. It also would be interesting to see how e.g. his reviews of the Malazan books would look like. I guess that he would be even more confused, and thus describe the story as even more pointless than WoT, simply because it's such long and detailed.

Even if there are - as a matter of course - slower parts in a work like WoT, I'm still overall entertained, because in my view there are gripping scenes in every book and I especially like RJ's ideas of "mythical engineering" (IIRC, RJ used this term) or the Pattern, etc. . Besides that, I'm convinced that there will be a grandiose finale in the last book. Of course, I'm aware it isn't highest literature, but in the end I think one can only judge WoT's worth after the last book is completed to see what was necessary and what redundant. However, it's clear that Roberts actually doesn't really care about seriously reviewing the positive and negative aspects of WoT, but is simply trying to make a few, mainly lame jokes or sarcastic comments.