At the end of the day, if a service becomes a haven for the most reprehensible people on the planet, that means it is both censorship-resistant and freedom-respecting. That is a good thing and it doesn't make it impossible to police illegal activity. Besides, IPFS is high performance, rather than anonymous. If you're a terrorist, child molester or drug dealer, then it is nowhere near as "suitable" for that kind of illegal activity as Tor, I2P or Freenet would be.
However, if you're wanting to share copyrighted content without the risk of takedown, it's totally perfect for that. It will revolutionise video sharing websites, reducing the cost of broadcasting extremely popular pre-recorded videos, while making the DMCA almost completely useless (as such websites can only delist but not delete content). Not only that, it will usher in an era of cheap hosting without the need for expensive cloud providers, as normies will now be able to partake in sharing files, unlike with BitTorrent.
Mainstream technology companies can still soft-ban illegal content on IPFS which people are almost universally against (like illegal sexual abuse images of real people and malware) if people can trust them to censor ONLY those classes of content. This can be accomplished by encrypted hash list checks using partial matching in the same way Safe Browsing Lists work. At the end of the day, the only reason the web is relatively clean of such universally unwanted content is due to well-respected blocklists combined with the use of technology like PhotoDNA.