You're optimizing for revenue/chance of success, not for the creation itself, which most world-class indie games are optimizing for (e.g. stardew valley, dwarf fortress, celeste, hollow knight, etc).

Also, building a million simple mobile games will not magically compound into making you a great complex/deep game builder.

Not trying to say your strategy is wrong, I just don't agree with your strategy if someone's goal is to build the game they have in mind, exactly like they have it in their mind (assuming it's more than a simple mobile game). It will help in terms of general "steps" to have built a couple simple games before sure, but that's about it.