Some people are comfortable with abstractions and paradox, others aren't. Doesn't much matter either way - seems more important to recognize that even if something doesn't make sense to us, it probably does to someone else.
I mean, on the whole I don't agree with Aquinas' argumentations, but when I set aside my usual map of the territory for a while, I get it. Or try to, anyway. Sometimes I fall a bit short of understanding maps of the territory that are radically different from my own. It can't be helped.
It sounds like you're not looking at the argument as an actual proof (or attempt at a proof, anyway), then.
I agree that it's useful as a glimpse into Aquinas's thought processes. He probably did think that this "proof" was a good reason to believe in God. When I look at it, despite it being confused and irrational, I can still take it as interesting in an anthropological sense.
But I'm also looking at his proof as, well, a proof: this argument is Aquinas's declaration that every rational person who agrees with his premises
must accept that God
must exist. And in that regard - i.e. in how Aquinas intended the argument to be read and understood - it utterly fails.
And the inherent contradictions do matter. As a logical proof, it would have been more valid to have said:
"since some maximally great attributes contradict each other, it would be a logical impossibility for them all to be manifest simultaneously in one being. Therefore, God (defined as a being that's maximally great in all respects) does not exist."
If your argument serves the opposite conclusion to the one you're trying to make as well or better than it serves yours, then it doesn't actually support your conclusion.
Aquinas has not provided us with an alternate "map" of the territory; he's provided us with partial
instructions to draw his map, but since they contradict each other, the map can't even be drawn yet.