Kellerman is just not fit to be a lead on a live TV broadcast, it is what it is. It's just not his skillset
He thrives better in a long form, slowed down form of media where he can flesh out his thoughts and give longer breakdowns. This is why his current show, The Ring Magazine Podcast, it's a longer 2 hour show. He's doing great at that. Also did Radio, great at that as well
His time on First Take was clunky. He's just not a natural with quick witted hot takes, couldn't make his point in under 2 min, and had no comedic timing, etc
You can also look at when he was on HBO Boxing on a live broadcast, he was always the 3rd guy on the mic