I definitely think Markovich's general approach is likely best for
long-term chess development.
I coached scholastic players for a number of years, and the issue was always going for immediate results, or long-term development. A lot of it has to do with identifying what the students are trying to get out of the game. Identifying the goals of the person learning the game is extremely important in determining the course of action.
If they just want to have fun, win games, and don't have any serious long-term goals I don't see a major issue with them being introduced to the French, KID, or any other number of openings. In the case of the high school team I coached, they didn't have chess goals after high school, nor was there really time to give them a "classical chess education", so they ended up using the Hanham/Philidor and Old Indian as black, and the 3. g3 Vienna as white. They did very well, but obviously that is far from ideal if they were learning for the long-haul.
If the player has long-term goals, then they need to start on the types of positions (ie: open) that dominate chess more so than any other, regardless of opening.
I know in my own personal development as a player I never had a coach, and had to rely on re-reading
My System and
Chess Praxis repeatedly. My original opening repertoire as white was the Nimzowitsch Attack (1. Nf3/2. b3), and as black was the French, Queen's Indian, and Nimzo-Indian. That's what I got exposure to from studying, and liked the most, so I went with it.
Those openings were all well and fine for a long time (carried me well over 2000 USCF), but then I hit a wall. Hard. I didn't have exposure to enough types of positions to continue making progress against opponents that weren't playing poorly in the opening. Sorely missing was the ability to handle open positions with fluid pawn structures. Over time I've remedied the problem, but undoubtedly I'd be a better player had that become second nature to me instead of closed positions, given the former is more common than the latter.
That being said, I do differ with Markovich on the timing of when the introduction to more closed openings should begin, preferring to start the process around 1600 USCF. Below 1600 they have a lot more things to worry about than the openings, because they're quite often still hanging pieces at that point, or failing to exploit the hanging pieces of their opponent.
Markovich wrote on 01/28/11 at 14:57:29:
Your King's Indian specialist will get blown off the board by the Four Pawns Attack, our outmaneuvered in a fluid system like the Gligoric. Or his opponent will just play the Colle and beat him with very straightforward Bd3, Re1, e3-e4 ideas. However if your 1900 player can sometimes beat 2200-level players in open positions (which would seem to imply that he's underrated), I will say fine, it's time for him to take a look at the French.
I can't even count the points I've won OTB facing club players (under 2200) and their attempts to play the KID against the Gligoric over the years. I haven't lost, or drawn a single game to any club player in that opening variation OTB.
An FM blundered on move
9 in it in one of my games due to being stuck in "systemic development" for lack of a better term. And this was at classical time controls over the board.
(1. Nf3 Nf6 2. c4 g6 3. Nc3 Bg7 4. e4 d6 5. d4 0-0 6. Be2 e5 7. Be3 Ng4 8. Bg5 f6 9. Bh4 Nh6??)