Do you actually fly that thing or is that just your assumption? The MiG-21 was known for beeing easy to fly compared to all other supersonic aircraft of the time and due to the good flight model this is neatly simulated in DCS. If you get used to not idling on the threshold and avoiding negative g for prolonged times, there is nothing else to bite you no matter how hard you throw the stick around.
Now beeing hard to master, I would throw in the MiG-15. While it is basically easy to fly, approaching maximum speed before loss of roll control needs a lot of attention and training. Without proper pre-planing of manevours you will lose control easily. Additionally aiming with two different gun types is hard.
Personally I find the MiG-29 and F-14B also pretty hard to master as both are really agile and fast aircraft but without FBW protecting you.