A big threat for illustrators is not LLMs per se but slop acceptance. We've seen the same with machine translation - it was (and to some extent still is) worse than human translation but people accepted it because it's free. I recently seen and ad on a street which caught my attention - it was a photorealistic image of a taking off plane. It looked off and when I looked at details it's become clear it's AI generated - the 1st giveaway - stationary turbines on a flying plane, an angle relative to the runway is wrong, small details, especially in the background are off. Someone prompted LLM, seen the result and decided it's OK to print this advert. IMHO they would be better off with buying a stock image.