It partly has to do with the fact that "Neopagan" and "pagan" are often used interchangeably and the meanings specific to each one get muddled, which can be incorrect depending on the context. When Neopagans are talking among themselves, it's OK to use them interchangeably because everyone knows what's meant and the discussion is on those modern-day practices that developed largely in the 20th century. But it does blur things when Neopagans and mainstream interact as it gets misconstrued with the mainstream term "pagan" as in what Abrahamic monotheists began referring to ancient/cultural traditions and led to the notion that "pagan = anything not Abrahamic" - which disregards the fact that ancient/cultural traditions didn't and don't self-identify as "pagan". Neopaganism is also NOT a continuation of ancient/cultural traditions. Some are reconstructions and revivals of ancient polytheistic traditions but most are, at best, loosely inspired by ancient polytheism but more directly influenced by Wicca and earlier Romanticism and Western esotericism.
Neopaganism is Eurocentric in origin and remained so for many decades with Greco-Roman, Egyptian, Celtic, and Germanic polytheism being the primary inspirational sources. In the 1980s & '90s there was a mainstream pop culture fad where Celtic was the in thing, with everything from TV shows like Robin Of Sherwood, music groups like Clannad, Capercaillie, Enya, and Loreena McKennitt among others were huge and the whole Riverdance craze was akin to Hamilton at its peak. The Neopagan scene reflected this fad and there was a noticeable shift from the more hippie ways dominant in the 1960s and '70s to "everyone" dressing like Renn Faire players, taking a "Celtic sounding" pagan/magical name and claiming some Celtic connection in one's practice. This is pretty much when Ecletics, the largest visible segment and the majority of which borrow from Wicca, began claiming "Wicca is Celtic" and set the Eurocentric image you're talking about. Eclecticism is still most people's introduction to Neopaganism and that initial influence often lingers even when people move on to something else. So it's often less obvious there were and are many POC Neopagans in non-Celtic-derived practices and traditions.
