Any emphasis on making a plan is very good advice. I still have my plan for what I need to buy when I can. But there are ways to do this without having an RO/DI at home, or even a skimmer. People need to plan what they can keep, and stay within those means (which is usually where they fall on their face).
Heck, then people buy a skimmer they can afford and all they hear from certain people is "that's a piece of crap, you need to buy this $200+ skimmer." Its frustrating to separate the fundamental advice from a lot of the attitude.
But to imply if you can't afford a skimmer and RO unit from the start (and what else should we add?) that you shouldn't be in this hobby at all is a bit overboard, IMO. Do they help? Most certainly. Do they make life easier? Most certainly. But should they stay away otherwise? I don't see why if they can afford a basic set up and only keep hardy fish and work up from there.
Keep a smaller tank, buy RO from the store, do frequent water changes...stay within your limits.
I wish I had all the best equipment from the start too, but it didn't happen, and it won't, I expect, for most people. I am far from the "best" equipment. When I started, I had a 10g with an undergravel filter, white aquarium gravel, and a hang on filter with some damsels. I knew NOTHING. Nothing about cycling or anything. That was 10 years ago. I killed a couple of things (mostly damsels), which was all I could afford, and learned from there. Now I can explain to people from the start how to do things differently, and they can start higher up on the learning curve. But if they don't understand the workings of a basic tank, no fancy fangled equipment will save them, IMO. It might slow the fall....
People who should stay away, IMO, are the one's who have all the money and think they can buy their way into what they want against all advice to be patient, etc. I think when you don't have a lot of money, you are forced into a certain degree of patience, and you may appreciate and research more of what you want.
Anyway, all I am saying is - if you can afford it all, get it. If you can't, know your limits within the hobby...make a plan...find the deals....but you can still be in the hobby.