It is absolutely possible to do it every time, but you need to understand why it is a hard thing to do. There are a couple of things to consider:
1st: main landing gear of MiG-21 is positioned way back on the airframe, behind center of gravity of the plane. So when you touchdown and the main wheel tires make contact on ground, there is some friction force. Combined with gravity force / vertical descent rate on touchdown, the result is the whole aircraft wants to 'trip forward' and slam the forward wheel on the ground.
2nd: the plane must be flown by the book! It is one of the hardest aircraft to master and its no wonder they only allowed the elite pilots of all military pilots to fly it because it can easily get ahead of you. What i am trying to say is dont exceed maximum landing weight. 800L maximum fuel without stores is the limit for landing. Not only there is danger that the tires may blow but the added above maximum weight is problematic - described in 1st point.
So how do you do it then?
Well once you practice enough it becomes easy. I usualy do the standard approach, established on final leg at 370 kph, about 320 kph / 80m altitude crossing inner beacon keeping about 12 units of AoA on indicator, slowing down to 280-290 when coming above runway, establish level flight 1m above runway, keeping 280kph and 12 units of AoA and then cutting the throttle to idle. At the moment the main wheels touch the ground i pull on the stick and keep the nose up (about 10 AoA) untill 240 kph and then slowly stop the pull and bring the stick to center to let the nosewheel settle on the ground. If i slam the NW at touchdown on the ground i consider it a bad landing.
The key is good throttle control to keep correct speed and AoA and to establish a 0m/s descent rate 1m above RW just before touchdown. Practice makes perfect.
To end this wall of text, here is a link to a short video of polish MiG-21's landing on a highway (i believe it's from a polish movie: Between earth and sky):
Well, they're not the bis version so i dont think they have SPS installed but in principle its the same. Note the elevator movement - the impulsive pull on the stick on touchdown, and not even they can keep the nosewheel in the air everytime.
Happy MiG-21 landings fellow virtual pilots. :joystick::book: :)