We leave it to each team to figure out what helps them balance flexibility with clarity to achieve their maximum speed of execution.
We do our best to have a common language around goals, strategy & measuring progress, but largely leave it to teams to figure out how best to build & ship given their own goals, strategies & roadmap.
This sounds to me like your sales team doesn't believe the target market is big enough and/or the right market. It's hard to believe in a product strategy unless you agree on who it's for, so the first thing I'd do here is to get everyone aligned on who you're building for & why, and then articulate why your strategy is the best way to win in that market.
The only stakeholder that must have buy-in for your product strategy is the one accountable for the results of your org or area. That may be a C-level exec or VP or GM or a discipline lead. Once they believe in the strategy as the best path to hit their goals for the business, what remains is largely a communication challenge.
Keep in mind that getting alignment with your primary stakeholder may require you to get the approval of multiple other stakeholders along the way. For my thoughts on how to do that, see the first question on the list.