If you want to write, you must read a lot is a useful advice. However, like most proclamations with an almost religious vibe, they have a long string of caveats and exceptions which, although commonsensical, cannot be packed along with the original statements without diminishing their gravitas. To put it bluntly, the advice only works if your read good material, and sometimes not even then.
Not only what you read has to be “good,” an adjective that implies value and, therefore, the ability to discriminate (something that terrifies a lot of people,) but relevant to your goal as an artist and your craft. Obviously, you are not going to learn how to write science fiction by reading Victorian romance novels or Nature Poetry (your descriptions of alien landscapes may be awesome, though.)