Can beneficiaries stop a named executor from ever being appointed, before probate is even granted?

Yes, there's a formal mechanism for this rather than beneficiaries simply having to wait and hope the named executor doesn't apply. An interested party who has real concerns about the person named as executor — for example, doubts about their capacity to properly handle the role, a serious conflict of interest, or another substantive concern — can file a formal objection with the Superior Court before a certificate of appointment is issued.

Filing that kind of objection generally prevents the certificate from being granted automatically; instead, the objection has to be addressed, whether that means the named executor responding to the concern, the parties working something out, or the matter ultimately going before a judge to decide whether the appointment should proceed as named. This is a meaningfully different situation than trying to remove someone after they're already appointed and have started acting, since nothing has been handed over yet.

Because an objection filed without a solid basis can be dismissed and may expose the objecting party to cost consequences, anyone considering this step should have specific, concrete concerns in mind rather than a general preference for someone else to be named, and should get legal advice before filing.