Zotero is, if you're not in the market for a closed source silo like EndNote, the only game left in town. Mendeley went full on Evil, and Papers for Mac is Mac only, closed source, and missing dozens of functionalities that are absolutely a must have in academic writing and research. An absolute must have is BetterBibTex ( https://retorque.re/zotero-better-bibtex/ ), which adds better Citekey management and, my perso…
My university offers EndNote (plus Web of Science and the Clarivate stack) for free for students and many of them don't use it - they'd rather manually manage the bibliography in their Word documents. The university even ran tutorials to show them how to set it up, add citations, and export the references, thinking maybe the students didn't understand the value of bibliography management software. Nope, even with the tutorials there was almost no uptake.
It turns out the problem was EndNote all along. I tried it myself - one of the worst user experiences imaginable, and I could totally understand why even doing references by hand is preferable. Eventually I told some of my own students that I use Zotero and to give it a go even though we're not supposed to endorse other software. Two weeks later most of them were using it.
So I'm actually quite confused at the fact that Zotero is offered as a free alternative to EndNote, unless the EndNote that I've used is some weird dated inferior version...