The Negroni is foul because gin doesn't mix with Campari & sweet vermouth, not because of the Campari itself, which can be a great mixer...unless you mix it with gin. A Negroni Sbagliato is 1:1:1 Campari, sweet vermouth, & prosecco (or any sparking wine). Granted, it is less boozy, but it goes down easy, and it is full of flavor.
Spring is upon us, so for some outside day drinking, you can have a Campari Spritz (2 Campari, 3 prosecco, 1 soda, on the rocks).
Or, try an Americano ( equal parts Campari & sweet vermouth, top with soda water, on the rocks). The Americano was the precursor to the Negroni, the latter drink coming about when someone with zero taste replaced the soda in the Americano with gin, and made the Negroni.
If Campari is too bitter for you, you can always directly swap Aperol for it.
Link: Liquor.com: Negroni Sbagliato