IGMP snooping is only for switches. Well, it can also be used with bridges, but I don’t see how/when that can be useful. On routers one should use IGMP proxy for similar purposes, which has been present in RouterOS for ages now.
Here, for instance. I’m sure I can find some more recent answers as well.
This is a user forum. If you need an official answer from Mikrotik, write to support@. This has been emphasized lots of times in various topics here.