No. But running a library in an illegal way is. Legal libraries pay the publishers.
But surely there’s an argument to be made that the people whose work goes into creating the texts you want to read have a claim to be recompensed for their labour. Authors, translators, proofreaders, layouters, illlustrators, printers and binders have mortgages or rent to pay and families to feed, and the servers and warehouses that store the texts are not free either. Where do these costs factor in to your »words are free to copy«-hypothesis?
But all those people aren’t publishers. The publishers are the ones owed money by Libgen, and the publishers can eat my shorts. The translators, editors, layouters, illustrators, printers and binders already got paid their wage/comission by the publishers. And besides, printers and binders aren’t making digital books, so bringing them into the conversation is bad faith nonsense.