I tested a few tags links in google search console, they were not indexed, this makes them almost useless.
Maybe the reason is that they are missing from the sitemap.
A link like posts_tags-sitemap.xml maybe would help.
And please there are so many tags, create an easy way to control them. From what i see too many people asking for this.
This is a bug and this has been already fixed in upcoming version. After the update all your tag links will be correctly indexed. The new version release is planned within next 1-2 weeks.