It depends on several things.

First, how do you treat your game nights? Do you treat them as a casual social gathering where it’s ok to show up fashionably late; or to not show up without warning; or to drop out last minute because of whatever non-emergency reason? If so, don’t be surprised players also treat it as something casual and social, and reading rules isn’t casual or social. Maybe D&D just is too complex and not the right game for your table if you just want to run a casual social event.

Personally I treat my D&D style campaign game nights similar to how I’d treat coaching a sports club. If you want to be a striker on a soccer team, and you don’t understand the off-side rules and don’t want to learn them, no coach in their right mind wil put you on the field either. Sure I give my players time to learn, and don’t expect them to know everything from day 1, but the absolute minimum I expect is a willingness to improve.

Practically, what I do for each player in my campaign is to compile a document which I expect them to focus on. They roll up a fighter, I will include the fighter class entry plus common special maneuver. They roll up a wizard, I will include the wizard class entry plus their spell book. They roll up a merchant (which I consider the most complicated class in my game and will discourage inexperienced players from taking it), I will give them the class entry plus a 101 intro to the economics of my campaign world. They have 3 months (approximate 10-15 weekly sessions) to understand the material I’ve given them, before I start reconsidering their presence in my campaign. Obviously there’s some flexibility, it’s not a life or death matter; but again I do expect at least some sign of willingness.

Next, please do understand I did specify campaign game nights above. Obviously things are different with one-shots like convention games or open table games at the local game store. I don’t expect the players to know any rules there and will happily guide them by the hand from start to finish.