As with all things, "it depends".
Momentum works well so long as you have enough alignment, clarity, and certainty.
When you don't know what you're building though, the last thing you want is a heads down project that you can't change course on or kill because it has too much momentum going in the wrong direction.
While it can be nice to throw something out there and play with it, I think a lot of the anxiety that causes people to feel that they _need_ to do that comes from the idea that "thinking isn't working." As an alternative, try validating early stages of thought work as being "real work" that's usually far more valuable than what follows.
Whiteboarding or taking notes can be a good proxy for thought work in early stages. Iow, those are good ways to "get something imperfect out" early because they are at a high enough level that they don't kill much time. However, hacking code out before it's been thought through tends to be a massive time suck.
I definitely agree that there's a shitton of value in hitting things regularly though (usually daily).
Snowballing. Sometimes it's ok to pick something easy, especially for a team, to get a small win first. If you're in debt, pay off the smallest amount first. Get the easy win. Build to the next.
And remember, you win by showing up each day, not by tilting at windmills.
This is good advice, but I struggle to apply it when many people are involved in a project.
If proceeding requires a review/input from someone, its a difficult balance between respecting their busy workload may mean they only get to it next week, or letting momentum die.
Funny, I wrote something with the exact same title in 2022: https://kodare.net/2022/06/24/optimize-for-momentum.html
Re AI: I find that Claude can massively help and massively hurt with this, the devil is in the details.