If “dynamic” in this context doesn’t equate to “agile/Agile” but instead to “chaotic”, first things first, figure out how to keep your head above water. Find out what you need to do to survive, but don’t try go in with the attitude that you have to save the sinking ship or anything; that’s a sure fire recipe for burnout.
While you’re treading water, take the time to evaluate what’s going on, and try to figure out why there’s so much chaos. Generally speaking, the main reason for chasing the shiny can be traced to an individual (or lack of an individual). That is, it might be a new founder/CEO who doesn’t have much experience, and while being a great IC, hasn’t figured out how to be a leader, and since the company is her baby, she hasn’t figured out that not everything is an emergency. Or maybe it’s the lack of someone filling a product type role and there’s no actual road map, no one is prioritizing anything, and it’s just chaos.
Regardless of the why, figure out ways to address that, work around it, etc, to try and add more sanity , whether that’s managing up and explaining how the churn is actually slowing the team down, finding someone to step up and fill a product role, maybe it’s just needing an engineering lead, etc.