You actually can. I recommend reading this article by Kit Walsh, a senior staff attorney at the EFF if you haven’t already. The EFF is a digital rights group who most recently won a historic case: border guards now need a warrant to search your phone.
Here’s an excerpt:
Like copying to create search engines or other analytical uses, downloading images to analyze and index them in service of creating new, noninfringing images is very likely to be fair use. When an act potentially implicates copyright but is a necessary step in enabling noninfringing uses, it frequently qualifies as a fair use itself. After all, the right to make a noninfringing use of a work is only meaningful if you are also permitted to perform the steps that lead up to that use. Thus, as both an intermediate use and an analytical use, scraping is not likely to violate copyright law.
The article I linked is about image generation, but this part about scraping applies here as well. Copyright forbids a lot of things, but it also allows much more than people think. Fair use is vital to protecting creativity, innovation, and our freedom of expression. We shouldn’t be trying to weaken it.
You should also read this open letter by artists that have been using generative AI for years, some for decades. I’d like to hear your thoughts.