Hi,
I'd simply delete all the ones that get no traffic.
Do the rest provide value? If so? Consolidate the rest into logical useful tags.
We have done this quite a few times and removing the bloat has positive impacts.
You can crawl the site after with something like screaming frog to find any 404's. You can create redirects for broken pages. This will make sure no 404's exist.
I hope that helps?
PS
If you don't need tags at all you can remove them from the index to test the water... If you have Yoast you can set tags to no index on this page: (yourdomain.com)/wp-admin/admin.php?page=wpseo_titles#top#taxonomies
Then if you don't need them and none are providing no value. Delete and apply redirects for broken pages if necessary.