Can't believe someone actually needs this explained to them, but here we go:
1. You said "I personally went off wrestling when WWE pushed Brock, Cena, Orton. I didn't care for it at all when I had seen Rock and Stone Cold." Dude, really? You think it's fair to compare every other top star to Rock and AUSTIN? Rock and Austin are the two biggest stars in wrestling history, EVERYONE FALLS SHORT OF THEM. THATS WHY THEY ARE THE MOST POPULAR WRESTLERS OF ALL TIME.
2. When Brock got his first monster push, he was on Smackdown. Smackdown was regularly beating Raw in the ratings back then, and Brock was working his fucking ass off. Brock got the monster push but I don't think there was 1 single person who, after watching Brock and Taker wrestle that HiaC match at No Mercy 2002, thinking Brock didn't deserve it. He was ready, he had the best manager in the biz at the time representing him, and he was putting on classic matches every time out, and along with Taker and Angle plus the Smackdown 6 was responsible for Smackdown beating Raw in the ratings and also giving us the best sustained stretch of television in WWE a history (Smackdown from 2002-2003).
3. Brock didn't get pushed at the same time as Cena and Orton and Batista. Brock had left the company by the time those guys got their push. When Brock was in the company, Rock and Austin were still there. So your argument is invalid.
4. WWE has booked Brock pretty bad since he came back. His first match back, he loses to Cena. Then he wrestles Triple H 3 straight times even though no one was clamoring for a rematch after the SS 2012 bout, and of course Trips beats Brock at Mania then they book a cage match where Brock has to utilize his superb selling to make Trips look strong in a loss. Then the do the best thing they have done with Brock since his return, which was the Punk feud and match. But then they book him against Big Show at RR just to screw the fans out of the match (why couldn't he have wrestled Bryan there????). Then he beat the Streak which I guess was good but the match sucked and I don't think there are many people who would say that was the right call. Then he squashes Cena at SS 2014 which was fucking awesome. But they screwed it up by having Cena come right back and squash the Wyatts 2 weeks later and then another Cena match at NoC which sucked as well. The RR 2015 triple threat was okay, and the zReigns match was great but the build for both sucked. Then they screw us out of ROLLINS match and put Brock with Taker AGAIN.
Bottom line, Brock should have come into the company hot out of the gates steam rolling Cena, Taker, Orton, and Batista, then use all that heat to make some new stars in Cesaro, Owens, Bryan, Ambrose, Rollins, Reigns, etc. That's smart booking 101. But of course WWE isn't in the business of doing things the smart way.
Last thought: blaming any single wrestler for the decline in ratings is stupid, even if it's Cena. It's on Vince/Creative to execute good angles and write great television, make new stars, all of that. They have failed miserably, and thus the ratings have fallen drastically.