There's several threads which seem to justify why Q&As for specific plugins / themes are harmful to WPSE, but all of the tags regarding specific plugins are still in circulation - is it not worth removing, merging, or making it more clear to first-time visitors that these types of questions are not what WPSE is for?
As far as I understand it this is actually the long-term plan but you can't just delete everything that has this tag as e.g. the question might also cover other stuff that is not off-topic.
But if you want to help speed up this process have a look at ♥ Summer clean up ♥
or making it more clear to first-time visitors that these types of questions are not what WPSE is for
Our tour page clearly states that third party themes and plugins are of topic. Also, I have already edited a couple of tags, and still questions get posted and these tags get used. You would be surpriced, it is not just newbies. A plugin recommendation question was actually posted by someone with 1K+ reputation.
These tags don't get read at all, or the people just simply ignore them. When you tell someone a question is off topic and tell them to read the tag description, they simply fight back and tell you their question is related to Wordpress, whether or not their question is asking to recommend a plugin/theme or third party support.
So, whether or not a tag is removed, it doesn't matter. For instance, woocommerce questions are of topic. What the asker do is, they use the plugin tag in stead thus trying to avoid their question being closed on the basis that it does not use the woocommerce tag.
My best advice will be, downvote downvote downvote. The reason, questions that is put on hold gets deleted immediatly when they are eventually closed on basis of downvotes, no upvoted answers and low views. They don't remain on the site as closed questions. I know you can't downvote at this stage, but once you get that privilige, use it to the advantage of the site
I think it would be worth removing, if all the questions under a specific plugin tag have been reviewed, plugin-contact-form-7 for example, then the tag itself should be considered for removal and all the non-closed topics retagged. That being said there's currently no way (that I know) to bring moderation attention to a specific tag for them to remove and retagging non-closed questions can become quite tiresome especially for bigger plugin tags.
Maybe we can create a topic specifically to track the plugins tags that are 'ready' for removal by the moderators and help in the retagging process.