Regarding Owen Hart, I think it was a mistake not to capitalize on his immediate popularity right after Survivor Series '97, when he was the "sole surviving Hart" and cut a promo about wanting to beat up Shawn Michaels not because of that "stupid piece of tin" Michaels had, but just to avenge his family, and hey, if he ruined Michaels's life by taking his gold too, that was the cherry on top. The crowd really reacted to it and Owen seemed revitalized as a character after having been a heel for the past four-plus years. I don't have a problem with him being shunted down to work against Jeff Jarrett and Triple H in the new year, but really, he should have had a two-week WWF Championship reign where he took the title off Michaels on a RAW and dropped it back to him at IYH: D-Generation X to take full advantage of what they momentarily had with him.
In terms of his work, he really was excellent up until his passing. Particularly, the Lion's Den Match he had with Ken Shamrock at Summerslam '98 was wonderfully paced with a nice "claustrophibic cage match" sort of thing going on as I recall, and though I might have to watch it again because I have not seen it in quite awhile, I think that it certainly was one of the three or four best WWF matches of that year (which I think is high praise because typically, the only really strong matches from that year in WWF are typically the mains on PPV, and so a mid-card PPVmatch being so very good stood out quite strongly to me).
However, Owen Hart was, for the most part, a career upper-midcarder in a major company, and I think that's about where he fits in terms of his talent level. I wouldn't call the whole of his career particularly disappointing. If he was going to go any higher, he would have had to be in a different time and place. It's a shame that he wasn't around when the WHC was a thing in the mid-to-late '00s. I think he could have done Edge's "transitional champion/opportunistic heel" gimmick MUCH better and with a better output in the ring than Edge did, in particular.