I think a lot of the failure is people not properly researching the Curly Girl method or all the information on this site, they only avoid silicones and sulphates. The method absolutely permits for low poo and that is often recommended here to newbies with scalp problems, fine or thin hair, weak waves or low porosity. It is a myth that you must co-wash to be CG.
It's also widely discussed on these forums that many more ingredients than just silicones can build up - butters, waxes including cetyl esters, petrolatum/ mineral oil, certain polyquats. An awful lot of us use the same product for rinse out and leave in conditioner, and again we do often suggest that to newbies. However too many have not understood that 'leave in' is short for leave in conditioner and instead use no conditioner but two styling products - another source of failure.
I have done as you say here - a lot of conditioner only styling and it was really helpful in understanding what different ingredients do for my hair. I do think more people need to try really basic products - a plain conditioner based on little more than the major emollients, a plain gel with a simple copolymer for hold, THEN consider adding in products laden with proteins, butters/ oils or potent humectants.
A Curly Girl friendly gel should be water based and rinse out with no build up or residue. A lot of people like lighter jellys such as flaxseed or okra, or make their own curl cream from a gel plus conditioner.