We are about to publish a new article on the subject:
#1: You are right, the Russians do NOT have the best air defense system.
#2: It seems that the Russians are not allowing the S3000 systems in Syria to work against Israeli targets. The IDF fight against Iran is not only something Russia is happy about - but also Syria
I think I read that the Russians gave Iran and Syria the S300 systems, not their most advanced, but withheld some of the key components and knowhow.