My Rosh Hayeshiva ZT”L didn’t believe in upsherins, but allowed anyone who wanted to give their children one to do it. My Rav does believe in upsherins- not as a chiyuv but as a minhag, and said there are pre-chassidic sources for it. My son didn’t have one, as I didn’t have one. Then I find out from my aunt that my father had one! Nevertheless, he doesn’t remember it, and I didn’t have one. Furthermore, while he had an upsherin, there was no “party” with catered foods and liquor. We did make my son a tzitzis party, as there was a mitzvah involved when he got old enough to put on tzitzis and keep them clean. The cynical side of me thinks upsherins became popular as an excuse to throw a party and waste money, like the “Sheva Brachos party every night” deal. I believe my rav quoted the Mahari”l but I will try to clarify for sure.
It’s not a chiyuv, it’s not avodah zarah, and don’t waste money you don’t have for it.