WooCommerce membership has no way of sending emails to members. You have to purchase the email followup plugin in order to be able to do that, but this plugin is a pain to have installed.
You could hav a list on an autoresponder which you maintain manually but this is not a good solution as well since users / members can simply unsubscribe.
There really should be a way to send an email to all members with a specific membership.
WishList member has this feature, memberpress etc.
It really should be a feature of the plugin, what is the point having customers / members if you can't communicate with them when something changes or updates have to happen to the membership plan?
I think that this is really important!