Here's the dirty little secret about "game design". Nobody designs a game from scratch. Not even the AAA games. Nobody just starts mashing out lines of code. For 1, it's criminally inefficient and would add YEARS to game development time. 3 Years is the usual AAA game development time. If they had to hammer out lines of code and all the bugs associated with that coding, they'd spend the first two years on just that. That's before they ever got to art design, game mechanics, world building, story, etcetera.
You see, the dirty little secret is that everyone is using an "Engine". Source, CryEngine, Frostbite, whatever. Why do they use an engine? Because it shaves YEARS off of development time. Most game companies buy an engine that someone else has already designed and then trains their programmers and devs in how to use it.
That's all RPG Maker is. It's an engine designed for ease of use to game developers who do not have a background in "mashing out code". You buy it the same as big AAA developers buy their engines.
A game company rarely develops their own engine as well. Maybe they used to, but not so much anymore. Usually, they contract it out to other people who spend their entire lives creating game engines to sell to companies, to make games with. It's big business to create game engines and sell them to corporations. Especially if they do neat things with graphics and physics and interfaces.
So, all you have to tell your parents or your friends, or whatever... Is that AAA game developers are using the same "cheat method" you are. They don't mash out games from raw code by hand. They buy an engine like you have, they program within the engines limitations, they change things within the engine that they can, and they hammer out a game the same way you are. The difference is that you're not beholden to anyone except yourself, so you can take more chances than AAA game developers. You're also more apt to read "game theory" and "player psychology" work than actual AAA game devs, because you're not programming for "The Lowest Common Denominator" playerbase. Namely, you can be more astute at designing a game than AAA game developers who only know how to work one program, or two programs, or how to work with a single engine, who are fresh out of school and only know about their field and not about overall game design.
Though, the question remains: "Is it important to know how to code in C++ or any other programming language?". Not really important, but it is useful. It's another color you can add to your canvas. In the same way it is useful to learn the Writing Craft or Art Design. These are things that add more colors you can paint your masterpiece with. If you could design your own menus or plugins, that could be valuable information for designing your own game, even if using RPG Maker.
But, is it necessary? Not really, no. Just like it isn't necessary for Animation Directors at AAA studios to learn about how to write dialogue for video games... or how to voice act. These places have teams with specialized departments and workers. If you don't have the ambition or drive to learn a programming code, then don't bother. Hire that role out if you want. You can, after all. Same with Art design. Storyboarding. Worldbuilding. Animations. Spriters. Composers.
Very few of us on these forums can do everything to do with game design well. Most of us end up hiring out for skills we just don't have, and have no desire/time to learn.
Honestly, the only reason to ever try to program something from scratch, is if you're going to be building an entire engine for game design that you plan to sell commercially. Learn the language if it interests you, but you should let your parents in on the dirty little secret of game design. Namely, that they have no idea what they're talking about.
