It's a (thoughtful) list for the "senior engineer in 500+ heads company".
If you work for a small startup (where you'll be forced to be "senior engineer" if you like it or not), you'll have no "manager", "peers", "projects", "hiring", "mentoring", "networking", and so 95% of the list items immediately pop.
projects = you’d have at least one (and smaller additions to the product that could be projects in their own)
hiring = you could be involved in the hiring process even though probably the CTO will handle it
mentoring = you can mentor others or get nentored by e.g the CTO
While I agree to certain extent, you still have these things in different shapes and sizes. Startup teams are a tight knit community in my experience, but as it scales, these aspects start to show their heads.
If you're at a startup you better be hiring! That's your #1 job! You better keep that bar high because the next round of folks will be hired by them. Further, at a small startup you can't get away from a bad hire, they're literally adjacent to you for 50+ hours a week.
Further to this point, networking is crucial too, but it's more networking outside the company. With other startups, with other technical folks -- your hiring pipeline is built on your personal network until you get to at least 20+.
As the CTO of a small-ish startup, this rings so true. All our employees were hired from our network. Its only now that we'll look for other sources to benefit or hiring pipeline.
If you work for a small startup (where you'll be forced to be "senior engineer" if you like it or not), you'll have no "manager", "peers", "projects", "hiring", "mentoring", "networking", and so 95% of the list items immediately pop.