my take on the subject, as someone who worked both in design and arts, and tech, is that the difficulty in discussing this is more rooted on what is art as opposed to what is theft
we mistakingly call illustrator/design work as art work. art is hard to define, but most would agree it requires some level of expressiveness that emanates from the artist (from the condition of the human existence, to social criticism, to beauty by itself) and that's what makes it valuable. with SD and other AIs, the control of this aspect is actually in the hands of the AI illustrator (or artist?)
whereas design and illustration are associated with product development and market. while they can contain art in a way, they have to adhere to a specific pipeline that is generally (if not always) for profit. to deliver the best-looking imagery for a given purpose in the shortest time possible
designers and illustrators were always bound to be replaced one way or a another, as the system is always aiming to maximize profit (much like the now old discussions between taxis and uber). they have all the rights to whine about it, but my guess is that this won't save their jobs. they will have to adopt it as a very powerful tool in their workflow or change careers
on the other hand, artists that are worried, if they think the worth of their art lies solely in a specific style they've developed, they are in for an epiphany. they might soon realise they aren't really artists, but freelance illustrators. that's also not to mention other posts stating that we always climb on the shoulders of past masters - in all areas
both artists and illustrators that embrace this tool will benefit from it, either to express themselves quicker and skipping fine arts school or to deliver in a pace compatible with the market
all that being said I would love to live in a society where people cared more about progress instead of money. imagine artists and designers actively contributing to this tech instead of wasting time talking fighting over IP and copyright...