You can build up Samoa Joe, Bray Wyatt, Roman Reigns, Dean Ambrose, Seth Rollins, AJ Styles, Kevin Owens, Sami Zayn, Baron Corbin, etc.. and Lesnar never beat Roman Reigns or Bray Wyatt before..
And like I said a thousand times already, I agree that he needed to be knocked down a level, but that honor deserves to go to someone younger. Imagine the rub of dethroning Lesnar going to a younger guy, and how much credibility and attention he would receive for his entire career. Goldberg is simply Goldberg, he doesn't need this; he attracts enough attention from his return by itself.
Sure, they can build him back up, but will he ever be at the same level as before his match with Goldberg? Doubtfully, he will still be booked very strong, just not immortal strong. But the opportunity to create a new mega star has passed.
Imagine WrestleMania 21 and HBK is the one to end Triiple H's reign of terror instead of Batista and Big Show is the one to defeat JBL instead of John Cena. This accomplishes short term ratings, but it does nothing in the long term.
Brock Lesnar is damaged goods now, not from the loss at SS, but from the positive drug test at UFC 200. He will never be seen in the same light again. Here you have this former UFC Heavyweight Champion, comes back for another go round and has to get on the juice to do it. He might have made a lot of money, but he damaged his reputation in the end.
So I'm not sure how much stock the WWE is putting into him anymore. He may have brought some UFC fans over to the WWE, but after UFC 200 they've gone back. Not even sure how much of a draw he is, he's rarely seen now, even less than before.
When Lesnar came back he broke the streak, demolished Cena, then took out Rollins and Cena at the same time. He's been through most of the roster and there simply wasn't anyone else for him to fight, like I said they had to bring back someone who was a match for him. Goldberg was that match.
This is the problem when you have someone like Lesnar. He destroy's everyone in his path, making the entire roster look weak in the process. Yes he could have been beaten by Reigns or Owens or Balor, but would it have been believable to the extent that it wouldn't have been shit all over. No it wouldn't.
Maybe this is the WWE's way to take Lesnar out of the equation and finally focus on some of their own guys, you know the guys who work their asses off night in and night out. Maybe it's time to stop with the part timer bullshit and let the roster shine, because when you bring in these guys, others end up looking like shit.