Because there will be millions of other people all making AI movies. And you'll be competing for attention with all of them in an attention lottery with seven or eight (nine?) figure odds against you.

The only original creativity will be in creating new formats and new kinds of experiences - which will mostly mean inventing new kinds of AI.

Everything made in an existing format will either be worthless or near as.

Same applies to software dev. Far more quickly than most people expect, it will also apply to AI dev.