Yes, that's it, you've nailed the primary complaints about Neverwinter Nights. First off, the OC is simply too boring, there's not enough memorable moments, and the quests are too dominated by combat, but not only that but that the combat is of a quite uninteresting nature, compounding the overall impression of boring.
But the biggest issue, by far, is the single character with one desperately frustrating uncontrollable companion. It's just not a scenario that's suitable for a single character game, it's a party-based structure but with an enforced solo-run. The optional single companion just muddies the gameplay as much as assist with it by having no permanent means to prevent them aggroing enemies at first sight.
However, on the plus side, it was the first computer game to fully utilise the 3rd edition ruleset, probably the most popular and beloved version of D&D ever transcribed into computer game form. This meant that NWN was revolutionary with it's build variety and character building options, especially when combined with the incredible itemisation. NWN's itemisation is still one of the best I've ever encountered.
And the radial menu, another truly brilliant invention that greatly enhanced playability and UI cleanliness without sacrificing complexity.
It's a shame you never found a campaign beyond the OC that you could enjoy, as there are many, many fantastic ones and I would heartily disagree with nearly all of the negatives for some of the campaigns.