Holy shit did the WWE fuck this up.
First off, I disagree that Sting was some "upper midcard surfer guy". While Flair became famous long before WCW was a thing, Sting is their only legitimate homegrown star outside of DDP and Booker T (who didn't become a main event performer until WCW's last year). The rest of WCW's talent was either pilfered from WWF (the entirety of the NWO), ECW (Raven, Malenko, Jericho, etc), or a hack like Goldberg (Austin lookalike who couldn't work a match if his life depended on it) or Buff Bagwell.
Sting wasn't the best in-ring worker, but he could pull off some sweet moves when he was younger and moved pretty well in the ring, especially compared to the majority of WCW's main event talent.
Here are the ways the WWE fucked up with Sting.
#1. Changing his entrance music.
#2. Changing his persona. They portray him as this "vigilante" who went up against HHH because he was cheating John Cena or something. He went up against Seth Rollins because he cheated to be the champion. Sting wasn't a "vigilante" in WCW, even though he seemed like one. He put on the makeup and went into the rafters because the NWO put some jobber in face paint and made him the "NWO Sting" and deeply embarrassed him. When Sting's buddy Lex Luger doubted him, he basically turned his back on WCW and became a "free agent". He didn't fight against the NWO because they were bad people, he fought against them because he was seeking #revengeance against Hulk Hogan for using an impersonator to make Sting's allies lose trust in him.
THEY SPENT A WHOLE FUCKING YEAR AND A HALF BUILDING THIS UP. We're lucky if we get three weeks to build up a main event match at a PPV these days.
Despite being great on the mic, they didn't have him speak once. Instead we get stuff like this:
What did the WWE do? Water him down as some old man Dudley Do Right who, 15 years after WCW's demise, decided to show up to the WWE because HHH is being a meanie. They changed him from "The Icon" to the "Vigilante" and fucked around with him.
#3. Jobbing him twice in a row. Ok, this is the one that pisses me off the most. He's had two matches in the WWE. The first, he jobbed to HHH like everyone has to do. It makes literally no sense to have him then job to Seth Rollins. It makes no sense and benefitted Rollins in no way. Instead of beating one of the biggest stars of the past 25 years, he beat some old guy who got beat by another old guy who wrestles only once or twice a year.
#4. Having him talk and explain himself.
Why not just something like this instead?
TL;DR - TNA did a better job with Sting than the WWE