For many decades (before smartphones) the phone system lacked human-readable names and yet was extremely popular with non-technical users. Similarly, most web sites probably do not benefit much or at all from a human-readable name.
A bigger problem with .onion is probably the fact it is accessible only via a system (Tor) that has significantly longer response time than a standard web site tends to have.
First of all, phone numbers were pretty short, and were chunked and thus pretty easy for humans to memorize. Do you think the average human will be able to memorize a bunch of onion addresses?
Second, even with phone numbers, companies used the corresponding characters to the digits to create human readable names, for example 1-800-FLOWERS