Robotyne is important as a rail hub and not much more. It would be reckless to risk an Su-24 airframe to attempt striking an infrastructure target at near max range. Even if the missile has a theoretical max range of 250km that could be affected by weather and more. There's also a chance that it's destroyed by missile defense systems or just misses the intended target altogether. So sacrificing an aircraft and it's pilot to destroy the Kerch bridge is likely seen as an unnecessary gamble.
It'd be smarter to ensure that you're able to strike other targets in the middle of the effective range from well within friendly airspace to protect valuable air assets. Then you can focus on holding what you already recaptured, slowly starve their southern troops of supplies, and continue to occasionally disrupt the flow of supplies across the bridge with drone strikes.