I love me some zeerust! Get me some zap guns and silver suits!
I love me some pixel art! Get me 16x18 sprites and palette-swapped wolves!
But it's not enough.
I know everyone has something to say on the topic of retro. Here's mine!
People get sucked into retro as a concept. It's enticing: it's less impossible than cloning one of today's big-budget games and less depressing than cloning one of today's grimdark scifi settings.
But, for some reason, ideas tend to stop at "retro". Because it's retro, that's all that it is.
A good example of this is every retro game ever created.
Wait, let me try again.
You have to want to say something. If you're making science fiction, you have to want to talk about society, about people and their place in the universe. If you're making a game, you have to show some interesting idea, some meat for a player to sink their thumbs into.
When people start from the idea of "retro", they rarely have anything interesting to say. There are a few reasons for this.
First, it's easy to think of that as a "concept" rather than a "constraint". Retro stylings are a constraint upon which your concept can be built, a "foundation" for your "house". But if you think about it as a concept, it is instead a house for you to decorate. You can still express yourself while decorating the house, but it has a lot less impact than designing the house.
It's easy to see this in RPGMaker games, most of which are literally the same game with the same graphics, just arranged with different color text and maps. While it can be a good exercise, it's not going to be an interesting game like that.
Second, even if you do create a unique concept, it's often mired in the old concepts from that era.
For example, there are a number of RPGMaker games that have slightly unique battle mechanics or setting ideas. However, because they are mired in turn-based "blob" combat and flat grid maps, the uniqueness is drowned out. The only people that can see the distinctiveness are people who have played so many RPGMaker games that they can no longer see the tint of RPGMaker itself.
Similarly, many people who make retro scifi comics or stories get mired in the concepts of the cheesy zeerust. Maybe we're talking about 5-crew cigar ships and zap guns that never kill anybody. Maybe we're talking about 10,000 crew superdestroyers and people that die at a moment's notice. Either way, those concepts weigh heavily on your story, and it's easy for your story to get lost in them. Especially if you lay it on heavy - for example, throwing in famous tropes and references to your favorite stories. Your unique, personal concepts are pale shadows.
Worse, many of those old concepts are extremely tired. For example, the idea of "magical, mystical elves" is painfully tired. When you put such elves into your setting, you are creating a bare spot in your setting, salting the soil so it'll be hard to grow anything of interest.
To be honest, I think these problems are what "Cerebus syndrome" stems from.
"Cerebus syndrome" is when a comedic story turns overly serious. It's common in webcomics, but also in Japanese manga/anime. For example, Fairy Tail is an anime that started off lovely and lighthearted, but turned slow, serious, and dark as it continued. Eventually it turned into a humorless version of Dragon Ball Z.
While Cerebus went dark because the author broke down, I don't think that's why most stories get grim. I think they get grim because they have to escalate. Escalation typically means exposing the characters to more severe challenges, which naturally results in darker stories. And they escalate because they've run their core concept dry: they can't "unfold the concept" any more, so they need "more of the same".
Fairy Tail's core concept was mostly "retro plus fun character design". That makes a great splash, but it runs dry pretty quick. So the escalation begins, and it gets dark.
A similar anime, Slayers, shows that this is not always the same cause and effect. Slayers has several series, and nearly all of them wobble unsteadily from light to dark and back again. This is because the fundamental setting has a lot of powerful concepts in it, but the concepts cannot be easily explored in "comedy mode". So it's not just escalation that causes darkness. Sometimes the core concepts are dark.
Still, all of that mumbling aside, the result is that you have to be careful when creating retro-flavored games or stories.
You can do it right. Shovel Knight is an excellent retro game that explores several fun concepts.
But you have to have a concept that you can build on top of the idea of retro. You can't simply take retro as a concept and decorate it. You need to consider what parts of "retro" support your concept, and what you need to cut away so you don't sabotage your idea with tired ideas and loud distractions.