Llamas can carry more 75-100 pounds versus 30 to 37 for a person.
Also people not working as pack animals can do other jobs.
Very true. But that's meaningful to the labouring class. It's not meaningful to the aristocratic class.
Aristocrats, or elites, just don't think in those terms. Even now, they don't think in terms of the well being of society, or the overall economy. They don't think in terms of social efficiency. An elite is completely happy to let coal miners die in preventable cave ins, or of preventable black lung disease, unless you can show them a direct benefit to themselves. Otherwise, they'll just divert funds to the next super-yacht and let people die.
So the simple fact of saving labour or greater efficiency for the wrong class of people is not a persuader.
Now, if you have a warlike general who needs to carry a lot of heavy packs and have hands freed up for murder, then sure, a population or a herd of llamas looks appealling. Something to develop. They can see an obvious, tangible advantage to their purposes.
A lot of the speculation and idea generation seems to consist of elite-fondling. That the way to get Llamas into cultures is by catering to elites - basically elites importing Llamas as fancy pets or personal zoo animals, etc. etc. But historically, Australia excepted, we've had literally hundreds of historical examples of these sorts of elite driven acquisitions, and they generally go nowhere and produce nothing.
Ecuadoran merchants are not going to automatically recognize Llamas as a valuable trade good, not on their own. From their point of view, Llamas are cheap and not worth transporting. They're not going to automatically assume that the things will fetch a high price.
You know who would recognize a possible value of Llamas? A meso-American sailor or merchant or visitor resident in the Andes, someone who knows their own culture, and can identify actual worthwhile exotic novelties that they'd know would go over back home, or who could see a useful potential in transplanting such an animal.
Alternately, another possibility - an Andean transplanted out into Meso-America, living there full time, lonely for a piece of home, and seeing advantages.
What you need are two things - first, a much larger volume of trade, around a basket of commodities, which will build up the skills and trading infrastructure, so there's just a lot of people with the skills floating around on both sides.