Israel doesn't seem to have been bothered too much by Syrian S300s. They do on paper seem dangerous, maybe there is a technical or tactical way that Israel has come to handle the threat. They may be very dangerous to an unprotected target or something that just blunders into its ideal attack envelope. Possibly becoming less effective in the face of HARM strikes - and they just don't dare switch them on.
I think a lot of the time they just don't switch them on - AFAIK Russia still maintained control of the S-300s they delivered to Syria and largely won't engage Israel.