Well, first of all, that "gross stuff" comes out of our bodies, and has done so for thousands of years. It's not really all that squicky - in fact, when it first comes out, it's pretty sterile, but that's neither here nor there. Your original question, about "do I have to use it" has a very easy answer -- and that is, "Not if you think it's disgusting."
The second part of your question, about whether people still use bodily fluids in spellwork, can be answered with a "Yes, some folks do." Although it's not used in every single magical tradition, there are a number of trads where the use of body fluids is considered perfectly normal and acceptable. Human fluids, be they blood, semen, urine, or whatever else you can think of, have long been viewed as having some pretty potent magical properties. If you look back at magical practice through history, the use of bodily fluids is nearly universal.
However, if you think it's repuslive, I'd simply recommend you don't use it. For more information on the use of bodily fluids in magic, read on: Body Fluids in Magical Practice.
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