I find the bundling of stack + startup success to be quite a peculiar sell. I wouldn't have considered the two that strongly linked - but I may not be the wrong audience for it.
Many RedwoodJS contributors have startup experience and we applied much of that in delivering features that often get lost in the rapid MVP pace where you have a small team and iterate fast ... only to face those decisions later. And it's not a surprise that these feature get left out early on: they take time and money -- two things startups have to manage from the get go.
Testing, logging, webhook support, setting up authentication, involving your designers more with Storybook, seeding data, mocking data, deploying, GraphQL best practices.
These are all common solvable problems that RedwoodJS has already thought of so you can focus on building a product.
I think a large portion of the early creators and contributors of RedwoodJS are people that were interested in building startups.
I've been down this path before, where claims of productivity gains to get you an MVP is true to a certain degree, only to have a giant web of wiring that creates implicit and explicit cognitive load, in my opinion, its like taking out a loan for an increasing cost of capital from rising interest and equity , where eventually, you can't hire, you can't debug, you can't reverse due to sunk cost since you've bet your horses on the shiny new trendy thing where you depend on other's opinions and their understanding of the problem which will offer no real benefits to your specific, specialized contexts. This is in fact the problem with many full stack or opinionated frameworks, it ignores the last mile problem.
As I grow older, I realize now the wisdom of choosing boring tech, when I was younger it was quite frustrating but now I see that PostgreSQL + Server side rendered language + Progressive interactivity is still strong for a reason and it is not Luddism or gerontocracy, it is stability from time tested collective experience of all minds. PHP is still going strong to this date.
At the end of the day, all tech stack, architectural decisions are economically constrained by time, capital and labor supply. An overly complex arrangement, especially one that focuses on novelty over what has worked and widely used, increases risks due to unknowns. Specific issues and challenges can be addressed in bite sizes, rarely do they require ripping out the established paths, instead of throwing in a dozen of new, complex dependency and opinion ridden web of tech that is highly novel & guarantees implicit volatile technical debt with false gains that require far more trouble than its worth.