I don't really know much about ratios and stuff like that. But it really sucks that the graphics aren't going to look as good as it should. It looks perfectly fine on my laptop i guess since the resolution is much lower. It just sucks that i can't enjoy it on my PC as well. i Just want to play it on a bigger screen Feelsbadman.
Well, 4:3 I believe is more commonly known as letterbox, that means it's mostly a perfect square. Think of 800x600, which for most japanese engines for RPG's and VN's is sort of the default. Now the most commonly used nowadays is 16:9, which translates to 720p/1080p/1440p/4K, etc. It's regularly known as widescreen since the screen is... well, wide, like a rectangle. There's other shit like 16:10 and so on, or those ultrawide screens.
Anyways, most (if not all!) RPGMaker developed games keep the 4:3 ratio due to the engine itself. I don't know the inner workings of the engine so I'm not sure if it can be changed but devs leave it like that due to that ratio being the default setting or if it's a setting they can't tamper with, at least as far as VX Ace goes. So because of that, the graphics (illustrations) are done in a 4:3 ratio, meaning stretching them just obliterates the resolution and creates jagged lines.
TL;DR Engine limitation, ???, profit?.