You can use your instrument the way you like, in your living room or for gigs, it is totally your thing and it is irrelevant what others think or say about how you use your stuff. There is no right or wrong in this, arrangers are considered as toys sometimes, however I am aware that many people make their living with this kind of instruments. I am open-minded as much as I can, and I try to accept that different times brings different music, different instruments, 100 years a go people used only acoustic instruments, today we use electronic very often, we simply evolve.
With that being said, there is just one problem with living room musicians who use arranger keyboards, and that is the fact that they are most of the time satisfied with less than the ones you call professionals, or i would like to say musicians who play arrangers for living.
This means that living room musicians are not pushing their arrangers to the limits because they do not need to, which is totally different for those who play for money and for other people, they need to use their arrangers efficiently and some small quirks can mean big problems when playing live. Not to mention people who create content for arranger keyboards, they suffer the most because they are unable to be creative because keyboard makers are getting false messages from majority of their users that everything is OK, and they only need to address some minor bugs in their OS.
We all use our instruments differently, and no one is right or wrong here. Just we need to understand each other, and have respect for both, musicians who do not want to use everything they paid for and are satisfied with basic stuff, and that minority that want to push the boundaries further and make Yamaha (or other makers) to give us more options, untie our hands to use our instruments the way we like, or create even better content.