A thing thats pretty stressful to engines and airframes even under normal conditions without having to stress them further with maximum loads. Its not like the Russians need more hard flying on their engines in the first place. Isnt that one of the main reasons for the ski jump?
Actually ski jump is way more gentle on the airframe during the takeoff than catapult. Catapult uses single point to accelerate an aircraft on full load during very short distance of +-100m. Giving up to 4g acceleration.
It is one of the heaviest duty on the airframe especially for tankers. It is actually more stressful than landing.
The ski jump is much more gentle. In fact virtually all land based fighters even with fragile gear like f16 are capable of ski jump. USAF actually tested it as an approach to handle takeoff from damaged airbase.
If you take a look on the simulation I posted before you'll see that the acceleration is quite low.