Commitment to co-founders is great, but commitment to your idea is a double-edged sword. It can lead to teams less willing to pivot because they're so committed to the concept they applied with.
(Source: Been on the teaching team of a few accelerator programs and seen founders make poor choices due to commitment to their ideas, despite advice otherwise from mentors and their market).
This is indeed double sided as most ideas will take years to fully flesh out. Not everything works out immediately. So while not pivoting is a risk, I believe it's equally risky to give up to early before fully testing your product in the marketplace. I find most startups are willing to abandon products before they launched to a real audience and/or due to negative feedback from industry insiders (people in the tech bubble).
Steve Blank always spoke about testing technology in markets and using that as the feedback loop. But I've worked with and also heard of stories of founders pivoting before they get to that point or after only testing a small subset of the market.
(Source: Been on the teaching team of a few accelerator programs and seen founders make poor choices due to commitment to their ideas, despite advice otherwise from mentors and their market).