You say it's more efficient but I think if artists were fairly compensated for their work, or at the very least had a say in the process, it would be too expensive or not have good enough output to compete. On top of that, it uses A LOT more energy - which should be enough to exclude it as an option considering the current trajectory of climate change.
Aside from that we need to consider the more philosophical question of whether we want to make creative dream jobs even more impossible to find. Should we degrade the public space even more with an avalanche of "good enough" imagery simply to improve margins for the executive class? Computers have already made every level of developed economies significantly more productive and yet individuals are worse off financially than they were in the 90s. All this pipedream of replacing workers with AI will do is relegate them to manual labour or lock them into some barely-enough universal basic income scheme.
[1] https://www.dacs.org.uk/news-events/artificial-intelligence-...