I think I've posted a reply in three of four of these similar topics before, but I think the issue comes up enough that it does merit repeating from time to time.
It isn't so much that "The RTP sucks and you're lazy for using it!" that makes a game good or bad. You will run into that opinion, most certainly, but it isn't really all that true. On Steam, however, that attitude is the norm because there are a lot of actually lazy people who just slap something together in five minutes, push it through greenlight, and try to earn a quick buck with it. So, the norm of "it looks like default RTP, so it sucks" is a little warranted. But, you can blame the "bad apples" for that.
As for whether or not it sucks... I tend to like the art style of the RTP in most cases. I'm just kind of a sucker for that. So, I enjoy using it, or using assets that look like it, quite a lot. You can do some pretty amazing things with it, too, if you're clever with map design. Not that I'm any sort of expert on graphic design or artistic flair in the visual medium, mind you, but I've made some pretty cool looking things with it in my opinion. I spent a fair amount of time, once, making a combination "bar/inn" with a stage with dancers on it and a staircase that actually went to the "top level" without using the single tile "staircase icon". Took me a while to make it look good and to get it right so that it didn't look like garbage... But, what came out, I was very satisfied with. I've also made some pretty nice house interiors with it as well. At least, I think they're nice.
But, all in all, I don't think it matters WHAT you use, so long as what you use is CONSISTANT. I've run into a fair amount of games that have "all custom content" and some of it is so horribly mixed and matched that there's no real defining art style and it loses depth and cohesion when your sprites don't match the surrounding terrain (think the weird chibi sprites from FF7 compared to the matte paintings they were walking on... that's not so much an art style as it is immersion breaking to look at).
All you really need to do is make what you have consistent. Make what you have look good and not lazy. Make buildings look used and lived in. Are there beds? A bathroom? A kitchen? Enough beds for everyone to sleep in? Enough chairs? What about outside? How well traveled is your path? It is spotty earth in places, or hard packed dirt? Are areas overgrown? How about weeds? Too many weeds to see flowers blooming? Or, is the place in town and there are flowers growing in a garden? Then, all you really have to do, is just make sure your objects and sprites sort of look like they go with your terrain.
The power of the editors is really staggering when you start exploring what they can do. Even without scripts. You can do some really neat things even with just animations for attacks and skills.