There's a middle case though. How practical an action is can vary considerably even among games that consider it possible. If the rules make something generally a bad idea, people will learn that pretty quickly and in most cases, avoid doing it.
What RoC can do is say "Yeah, the general application of the rules here would make this look dumb compared to just spending the round closing with them, but its cool so we'll finesse the rule here."
(You can argue that what should be done is a more general massaging of the rules to make more cinematic actions more practical in one way or another, but the hobby is full of people who will just end run problem spots in the rules they hit rather than ever formally, or even consistently informally, house rule them. I find that a little incomprehensible, but different people's minds work differently).
It's absolutely a spectrum and a fair amount of the rules are left purposely vague so people can implement what makes sense. But, for example, the OP's DM allowed a standing jump that more than doubled how far the rules allowed assuming someone 7 foot tall with a 20 strength. With a high enough athletics check, I might allow someone to grab something a couple of feet higher (the jump itself on gets 4 feet) but that still gets you grabbing something less than 20 feet up and that's the optimal outcome.
What would be especially egregious to me is that another player had spent the resources and implemented a set of actions by leaping from pillar to pillar to get high enough to leap on top of the dragon. Then the next player goes "Hey, I'd like to be up there too!" and the DM gave them magic jumping abilities.
Giving someone magic jumping abilities because it's cool is fine if that's what you want out of a game. But I've been in games that did something similar and it was basically one person was the most convincing and didn't give a s**t about the rules got a massive power-up. Those of us that like the way the game works were just left with the choice of trying to be as convincing as that person and not playing the game showed up to play (it was a convention game). The restrictions my character has, and finding ways to be successful anyway, is a big part of the enjoyment I get out of the game. Happy fun hour based on cool descriptions and hoping the DM plays along, is not.
All this should be discussed ahead of time during a session 0 or even earlier.