One thing that I had never quite understood until recently is that 5th Edition of Dungeons & Dragons is so malleable. It’s like you get this giant rulebook and you learn how things work. You don’t have time to read it cover to cover, but let’s be honest, nobody does. In fact, it wasn’t even meant to be read like that, even for dungeon masters. The rulebook is just there to provide you the blueprints for the building you and your friends are creating together. It tells you how to set up the scaffolding and presents a rough idea of where to go from there, but really, it’s not an instruction manual. The Player’s Handbook is meant for reference— solving disputes in a pinch, or understanding the idea behind a rule, but it isn’t set in stone.
Matt Colville summed it up pretty well. The book is not D&D. D&D is what happens at the table with you and your friends. As a matter of fact the book isn’t even a necessary part of that journey. You can have a totally valid game of Dungeons & Dragons without any book or physical dice, because in the end, D&D is what you make it, so it involves a lot of imagination.
All that being said, the most important thing is for everyone to have a clear understanding of the way things are supposed to go. I break and bend rules all the time. Being a DM is about making calls others would disagree with. My brother likes the idea of casting Eldritch Blast (basically a laser beam) at targets 300+ feet away. The rules allow him to do this, but I interpret this to mean the spell can remain effective at that range, not his ability to aim. So while I would allow him to attack, it would be at disadvantage. At the same time, though, there’s nothing in the book that says how Eldritch Blast is cast. For all I know, it has nothing to do with one’s ability to aim, but that’s how I rule it, cause that’s how it makes sense to me.
It doesn’t always go poorly for the players, though. Spending hit dice to regain health is “Roll 1d8 (usually) + Constitution modifier”. Theoretically, if a player has a negative Constitution modifier, that means they can lose health in a rest. There’s nothing in the book that says spending hit dice gains a minimum of 1 health (unless I missed it), but it makes no sense to me. So I house ruled that to say your Con mod can only benefit you in a circumstance like that.
All games of Dungeons & Dragons have house rules. The game is too complicated to function without them, and people who are super strict about what the book says and never give the players any leeway tend to be a little awful to play with anyway.
So as Captain Barbossa said, “The rules are more like guidelines”. I often say you can break a rule once you understand why it’s there, but in this circumstance, you might not even need that. Remember, everyone’s fun is paramount. If somebody is having less fun because of something they don’t agree with, what takes priority, the fun, or the rules obstructing it?