Summoner is definitely on the more complicated side of things, as not only do you have to be concerned with your rotation, there's a ton of nuance when it comes to understanding how pet AI works. I kind of put the blame on the resources that players have created to teach others the job though. Too many of them go for a top down approach trying to get you to do this or that exact rotation, or perform optimizations that only matter at the 99th percentile, instead of building things up from the bottom with the basics and holistic knowledge.

That said, I don't think it's necessarily a bad thing for summoner to have a harsher difficulty curve than other jobs. Just look at black mage and how people take pride in it being a job that heavily punishes you for mistakes, not only for the sense of accomplishment it gives, but as justification for the amount of dps they do. There's no reason summoner players shouldn't be taking pride in mastering a difficult job too. Between blm and smn, these two jobs are both at the top of their game now and certainly deserve it.