Yup, back in the good old days when DMs weren't allowed to alter or ignore rules. Oh wait...
There are two questions here that I'm finding interesting. 1) Are rulings in some sense superior to rules? 2) Does whatever we decide about 1) entail that rules mean anything we want them to mean?
In looking at those questions, I ask other questions like - why buy rule books? what allows us to recognise a D&D game as a D&D game? what did we want from rules anyway?
My working premise is something like - Rules are a stable and meaningful foundation. They continue to have meaning even if we can alter or ignore them as we choose. We can have meaningful, resolvable debates about rules. A claim that rules mean whatever a given DM wants them to mean is not only unhelpful, in terms of the analysis of rules, but also false. A DM can alter or ignore the meaning, but cannot erase the meaning. As an aside, I think their meaning can be erased through removing them from context, i.e. rules only have meaning, given context.
What [MENTION=2525]Mistwell[/MENTION] said, with a little extra.
I would say there's a line between a ruling and a house rule that most people would recognize (not all, this is the internet of course). How you handle jumping an "unusually long distance" for example is a ruling. The rules are silent on the subject other than to say that sometimes it can be done. It gives no DCs, no instructions on whether you just state your character is going to jump further than usual or need a pogo-stick or roll a percentile die. So how it happens IMHO is a ruling.
I make a ton of rulings all the time. It's just part of running a smooth game and can change the flavor of the game without changing core assumptions.
On the other hand, I have a handful of house rules for when I explicitly override the clear intent of a rule in the book. For example, I've always thought the way certain items replace ability scores instead of enhancing them is dumb. A two year old should not be able to but on a belt and be able to lift a horse. So I have a house rule that gauntlet of ogre power, belts of giant strength add to your strength (with a max) but they don't replace it.
There are gray areas of course. I have no problem with someone ending a turn mid-jump when they run out of movement. I don't consider that a house rule because I don't follow twitter and the rules don't clearly state it one way or another. But I don't really care if someone else considers it a house rule. They're wrong of course, but they're entitled to be wrong. [Kidding. Mostly.]
My preference is to stick pretty close to the base rules because they work reasonably well most of the time. When I start a campaign I have a session 0 and discuss my handful of house rules and go over some rulings that come up on a regular basis because people want to play D&D, not Oofta's Amateur Hour RPG.