I don't think you come off as unintelligent.
People always have gaps in their knowledge, topics that are harder to focus on and retain information about, etc. Even very intelligent people will have areas that they're subpar in; someone of average intelligence can have topics they understand in great depth.
If there's topics one finds so dry that it's impossible to give them enough attention to retain knowledge on, it makes sense that one would likely be weak in discussions that involve those topics but it doesn't mean that person is dumb. At most it might mean some of their current positions aren't very well-substantiated and might change if they engage more with those topics.
Someone who lacks the insight to recognize some of the weaknesses you mention would appear less intelligent than someone who doesn't recognize short-comings they possess. One must have at least a degree of insight in order to avoid falling victim to Dunning-Kruger effect after all.
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