It's not that nobody can do what battlers do, it's that it takes a minute to adjust to the format of current battle rap. Like anything else, you have to do it often to get the feel. That's why even if Cassidy and Jag don't die, they still look very amateurish in their delivery, performance, and way they set up their material. Jag is a little bit closer to modern day battle rap in how he sets up his lines, but he's still more of a beginner. Cassidy does not sound right in current day battle rap format.
Because they're "industry" rappers, they will face battlers with big names rather than battlers that are actually the most talented. Ars, Goodz, Math and Hitman are not known for having elite lyricism, and they also battle infrequently they're even a little bit outdated in modern battle rap terms. Red is the only one that would be considered an "elite" pen, but Red is also known for being very hit or miss most of his career. And mostly miss when he's put in a big situation.
Cassidy and Jag can survive against those types, because even though they have certain nuances to their styles, and a better grasp of what's happening now, they're still not what people would currently consider "elite" outside of their names.
Jae Millz came back against a 60% K-Shine and died very badly.