We definitively need these tags, the more exact a search result can be narrowed down, the better. Some would argue that all of those tags could be ignored and simply tagged Modeling.
from the basic description of all tags
A tag is a keyword or label that categorizes your question with other, similar questions. Using the right tags makes it easier for others to find and answer your question.
Although a question about the knife tool could be tagged modeling and left at that, you could further tag it as knife-tool and make search results much more useful. however, that same question it would not necessarily also be about extruding, so I would argue that not only those three, but many more like them could be added. when you broadly tag something modeling, it can have Many, Many different questions that have nothing to do with each other. tags are meant to categorize questions that are similar so someone with a problem can easily find his/her/its solution.
This is the same situation with the modifiers tag and the subdivision-surface tag. someone could blindly throw on the modifiers tag and walk away, but it makes it much more difficult for an expert on a certain subject to assist that person.