Just my opinions but I thought the stoppage was good. Could the ref had let it go long, and have we seen refs let it go longer in the past? Yes. Have refs stopped fights when a wobbled fighter eats a barage of punches and finally gets sent to down (but not fully out)? Yes. We've seen it both ways but Izzy getting back to his feet without his full balance, and being wobbly on the stool after is enough for me, he was done. His brain was rattled, I don't always need to see a fighter eat 5 more shots and end up unconscious face down for 10 minutes, this is the exact reason TKOs exist. Stoppage was fine.
Opinion on the fight is that Izzy could easily have won the fight with another takedown in the 5th. He proved he could control Alex on the ground without much trouble. But instead he decided to follow his ego and prove he could stand with him. One of the rare cases of a low IQ decision from Izzy. You don't give the guy who only has a punchers chance, the chance to punch you. Congrats to Alex though, he did exactly what he needed to do.