Pretty reasonable thoughts here I think!

It's true that being at a company where everything is abstracted from you makes it hard to step out on your own where things aren't abstracted and you have to do all the dirty work yourself. Also true that working on only one part of the stack forever means you may not have the diversity of skillsets to build out a product e2e fron scratch. I've had this same experience at [large SV company] and honestly going to a rocketship startup where I started as one of the first couple hires and being there through the 500th hire helped give me so much more of a diverse set of skillsets (FE, BE, DevOps, Sysadmin--even setting up the wifi at the offices!) and visibility into the business and fundraising side of things, getting to work with the top VC funds in the world to see how they think.

I haven't started my own thing, but the experience at the fast growth startup gave me the confidence and skillsets I would need to start my own thing, and those skills largely track the main points of the article.

That is the difference between a company that cares about you and a company that only cares about profits. I fully train my employees and wish them the best no matter where they end up.