The lean startup approach doesn't advocate spending a lot of marketing dollars showing people your MVP. It advocates being, well, lean, until you have a good reason to believe that you have "product/market fit". It's then that you crank up the marketing/promotion stuff.
After all, wouldn't it be a disaster to spend a lot of expensive marketing dollars showing people a product that they don't want or need?
EDIT: i guess my point is, engineering isn't cheap either. Shouldn't be OK spending that money ahead of product fit either.
The whole point of the lean startup approach is to posit that the "business school approach" is wrong, exactly because you don't know all this stuff ahead of time, and that "business plans" are an outdated idea.
And if what you're doing is a truly novel product, then you almost certainly don't. If you're using the "fast follower" strategy to be the nth company doing a product in a certain space, then sure.
OTOH, even Steve Blank says that there are certain areas where you don't need to do Customer Discovery / Customer Development... like, if you're creating a cure for cancer, it's pretty much all engineering. If you build it (and it works) they will come. But I think that kind of scenario is the exception, not the rule.
A startup is "an organization dedicated to creating something new under conditions of extreme uncertainty" (quoting the insider cover of Eric Reis's The Lean Startup). If there isn't extreme uncertainty, then it isn't a great fit as an overall strategy.
On the other hand, the LS counterpoint would be that you'll miss considerable insights if you rely on existing knowledge/research (Ford's classic "If I asked people what they wanted, they would have asked for a faster horse" quote....)
“The Marimba Phenomenon is very hard to avoid when you spend too much money trying to launch a new product. It’s easy to spend on marketing and PR, since that just takes cash, but it’s hard to spend on software development, because that actually takes time and talent.”
“By contrast, small companies that don’t have great marketing budgets are in a great position to launch early and often.”
https://www.joelonsoftware.com/2005/11/02/massive-frontal-pr...
Any pivoting in the business strategy means you don't know your business space. Business opportunities and the required value-add features should be painfully obvious if you have experience and know the industry/niche.