I've worked for startups, both under an agency and as a contractor, and IMHO the problem isn't how well a startup executes, it's how much runway it has. Or some combination of those things. We can always gain experience and improve our execution, but funding is (sadly) still an open problem.
I adore HN obviously, but am concerned about the idea of mentorship as a prerequisite to success. Truthfully, I was far more clever fresh out of college at 21 than I am in midlife after learning how to supposedly do things better. All I needed was any money at all to work on my own projects (something like $24,000 annually in the year 2000) but nothing like that existed. We didn't even have Kickstarter. So I worked a bunch of dead end jobs making rent and all but wasted the most productive years of my life.
But there have been several changes over the last 20 years that removed the artificial barriers to entry that kept me and makers like me on the outside. The main one being the JOBS Act of 2012:
https://www.investopedia.com/terms/j/jumpstart-our-business-...
Because of that, non-accredited investors can invest up to 10% of their income:
https://www.startengine.com/ (no affiliation)
If I were starting out now, I would largely ignore what other people are doing, and figure out a way to raise 2+ years of income, or at least $100,000 per person, by checking all of the boxes needed for crowdfunding. Then show the campaign to older people who have some disposable income that want to invest outside usurious and rent-seeking systems like stock markets and real estate.
Then I would use something like a referral program to bootstrap:
https://andrewchen.com/how-to-design-a-referral-program/
https://www.coldstart.com
Everything else on the technical side is honestly pretty easy to figure out for programmers. There's just not that much to learn, it's mostly about balancing process with pivoting to make steady forward progress each day. Two-person teams have been more productive than entire companies.
And nobody wants to hear it, but, I feel that up to 90% of "best practices" today are about working around fundamental inadequacies in our tools which still haven't been addressed. For example, all databases needed event streams (like Supabase) so that we could have had reactive programming from the beginning. Jira and countless other similar tools have just not kept up with their errata. The level of expertise needed to set up cloud deployments has passed the point of believability. Native mobile development probably shouldn't be a thing, except for certain performance-critical components. And so on.
The big opportunities today are probably NOT in the typical high-effort approaches common to startups mired in scaling issues. We can look down the road a little and bypass those eventualities, assuming that we can scrape up enough funding to work independently and avoid groupthink.