That is your opinion. The data supports another opinion.
Fight Stats: Double Leg Is The Most Common MMA Takedown, Nurmagomedov Most Successful Takedown Artist
This article looks at 799 MMA fights with 2072 successful take downs. They break down the number of each type.
"The top was the double leg takedown. It accounted for 37.4 percent of all takedowns recorded. In fact, the double leg accounted for more takedowns than the single leg, outside trip and bodylock combined."
From their data double leg accounted for 798 take downs, followed by single leg for 353 take downs. Hip throws only were used 63 times. (I like hip throws
) O'soto Gari, your "diagonal cut," accounted for 13.
Your first video showed O'goshi (hip throw) and you were worried about being hit with his left hand. You were watching a teaching demonstration with pauses in the motion. The very first part of that throw is to off balance the other guy forward and to his right. There should be very little weight at all on his left foot, and his posture should be broken. At this instant, he can generate very little power with that hand. An instant later, his feet are off the ground. From this point on, there is zero power to that left arm. (in order to generate power, he must use physics... he must push off the ground to generate punching power, but his feet have already left the ground)
The empirical data shows the double and single leg take downs to be the most effective type of take down... even if they are using arms to deal with legs.