I agree, they tend to pollute and get messy. I don’t use tags as ways of categorizing things. I use a small number of curated tags to act more like special status indicators. For example, I have a tag to indicate that I am still processing the notes for a book. Once I’m done, I would delete that tag.
I wrote some ideas about tags here. I use more than these, but that is the general idea I use for tags.
I do a lot of project management in Notion as well. And there too, I only use the tiniest handful of tags for special purposes. Usually to flag things in a specific and temporary way.