From personal experience, I can attest to the fact that even the most scrupulous wearing of masks, whenever and wherever proscribed by Regent onboard the cruise, is NOT going to guarantee you or protect you from possibly testing "positive" for Covid while onboard. Relying upon mask wearing, by you and others, to "absolutely protect you" from Covid might only provide you with a false sense of security and is probably more "bother/annoyance" than it's worth.
If testing "positive" and/or becoming symptomatic for Covid while cruising, along with the attendant/required quarantining regimen, is worrisome, stressful, or unacceptable to you, then you should probably seriously consider delaying any upcoming cruises until conditions further clarify and resolve themselves. Regards.