The web wouldn't be as accessable, though it probably won't hinder anyone, as it's similar to having to type a phone number by hand.
Are we talking IPV4 or IPV6? If the latter would be the case, have fun...
Though bookmarking would be a more common technique then, an almost irreplaceable way to browse the favourite sites.
One great thing (or less great?) would be to type a random number in the browser and land on some random page. That's a bit harder to do when typing random words in the address bar. Lots of site names haven't been taken.
But spammers would stay spammers. Like this technique: gogle.com googl.com for example. Hope for typos to happen to redirect innocent people to spam sites.
The priciest domains would be four of the same digit (IPV4): 10.10.10.10 or 191.191.191.191 for example.
... people would probably maintain their own hosts files ...
That would be very messy, unless it would get united in one commonly used hosts file. And there we have ICANN and all the others again.
I've heard stories about people phoning John Postel, telling him the IP address of their site, and he maintained the global hosts file by hand.
And those without fixed IP addresses would still be second-class netizens, rather like those who don't have their own domains and personal websites are today: powerless and dependent on corporate-owned platforms.
I think the "dynamic DNS" would have to look like this:
127.0.0.1/starbreak/index.html
127.0.0.1/geese/index.html
127.0.0.1/melone/index.html
Or at least that's how a Neocities-like website would solve it.