I understand the frustration some users have with it. In a real jet, it's a pretty simple process to reach forward and raise the big red handle without ever taking your eyes off whatever you doing, like flying off of your lead. It's another thing to have to play the guessing game of is it R-Shift-G, L-Shift-G, L-CTRL-G, etc, especially if you don't have the time to stay as proficient in the MiG-21 specifically as you'd like. But, I can also understand the intent of making all functions bindable.
I'll echo what NeilWillis said and recommend investing in VoiceAttack. After rotation, all I do is say "Gear up, flaps up" and it will do the appropriate key presses to raise both. I have similar functions set for gear/flaps down, Ground Power On/Off, re-arm menu, and chute deploy/disconnect.