A lot of good responses here, but they're all missing the core problem from your post:
> business team is constantly changing priorities based on new client requests
If you have a separate "business team" that changes the priorities, they are managing the roadmap, not you. If you have a situation where you are accountable for the roadmap but other people get to make all of the roadmap decisions, you are in a very difficult position. The most important thing for you to do is focus on communication and clarity.
If you aren't already, you need to be tracking everything from week to week. Record a snapshot of the priorities on a given week, along with any "business team" inputs that change the priorities. You need to be able to show in detail where each priority started, stopped, paused, or was re-ordered. You also need to be able to show who directed the priority change. Work on a report or slide format that can clearly show how the priority list has evolved over the course of the year, and don't be afraid to put names next to each priority change ("Moved to #3 priority on Mar. 3 after request from Bob").
If the priorities are constantly churning to chase whatever client requests are coming in, the sales team has hijacked the PM process for their own personal gain. The best way to push back against that is to shine some light on it by tracking it, visualizing it, and communicating it with leadership. Once you make it clear and obvious, it's much easier to get leadership to clamp down on priority changes and drive toward some commitment.
But as long as the business team can quietly reshuffle the priority list each week and let other people suffer the consequences, nothing will change.
> business team is constantly changing priorities based on new client requests
If you have a separate "business team" that changes the priorities, they are managing the roadmap, not you. If you have a situation where you are accountable for the roadmap but other people get to make all of the roadmap decisions, you are in a very difficult position. The most important thing for you to do is focus on communication and clarity.
If you aren't already, you need to be tracking everything from week to week. Record a snapshot of the priorities on a given week, along with any "business team" inputs that change the priorities. You need to be able to show in detail where each priority started, stopped, paused, or was re-ordered. You also need to be able to show who directed the priority change. Work on a report or slide format that can clearly show how the priority list has evolved over the course of the year, and don't be afraid to put names next to each priority change ("Moved to #3 priority on Mar. 3 after request from Bob").
If the priorities are constantly churning to chase whatever client requests are coming in, the sales team has hijacked the PM process for their own personal gain. The best way to push back against that is to shine some light on it by tracking it, visualizing it, and communicating it with leadership. Once you make it clear and obvious, it's much easier to get leadership to clamp down on priority changes and drive toward some commitment.
But as long as the business team can quietly reshuffle the priority list each week and let other people suffer the consequences, nothing will change.