I have had 2 Google groups (under a GSuite/non profit) since 2013. I can direct add and remove members. It's an excellent mailing list and offers expansive storage for our attachments to emails. One group is used for our Board of Directors and one is for collecting and distributing publishable news items as attachments.
Their spam filter doesn't disappoint and the group is painless to manage. Users within our group have no need to create or maintain a password. I can add users by their cell phones and email addresses which need not end in @gmail or be associated with a Google account.
The current free version of GIO would not tempt me to move from Goodle Groups because of storage limitations, the uncertainty of future GIO pricing tiers and loss of features. Google groups is a known service, it's stable and it's free.
I agree heartily that Google Groups is not for everyone, nor will it serve the needs of most or many. But it does have a place for us as an educational non profit with minimal revenue where we need control over members in a forum. It works quite well nested within our domain managed GSuite/Google Works framework.
It's far from perfect but it is free and for the above reasons, I would not advise it should never be considered.
ASG Volunteers Group.