>>507617050
You can't just fly them over and start shooting. As jets grow in complexity, so do their requirements. MiG29, especially the hydraulic models, can just come down and go up wherever. A Su57 needs to have its entire support network coming along and transferring one takes like a year if you rush it. Except one isn't even worth transferring, you need an operational squadron to get the effects you want.
This is why Iran doesn't even have Su35s yet.