This is gonna be long, just so you know lol
I formed a theory shortly after playing some Shantae. It's not much and the theory just suddenly came to mind, but I think the games may take place somewhere in the distant future. Some of the dialouge in 1/2 Genie Hero and Seven Sirens, coupled with how the environments look kinda makes me feel like these events are happening long after something took place in their world. I know Rotty mentions going on the web in Risky's Revenge, but that was more of a visual gag. Even in their world full of magic they still rely on technology, and there are direct references to somewhat more modern things that we have in those 2 games specifically. In 1/2 Genie Hero near the beginning of the game, Shantae talks about reading comics and eating ice cream, and in the 100% ending Uncle Mimic mentions unearthing something related to a bicycle, which makes me think they were something people already invented but stopped using for whatever reason. In Seven Sirens, part way into the game Sky's "boyfriend" and Squid Baron make a deal with each other, so Sky and Shantae are sold as mint condition toys to Squid Baron. Selling items online, especially things like plushies or action figures is something that's quite common on sites like eBay, but also something people have only been doing fairly recently, and may have been something that carried over from long ago. Again, this isn't much, but still. The reason I feel like the environment gives off this "distant future" vibe is because of 2 things. #1 There aren't very many people around, and a majority of the lifeforms you encounter are very strange looking, some even humanoid but not fully human. The most people we ever really see are in Seven Sirens when people gather in the stadium to see the half genies, but even then it's most likely only a few thousand people at most. The lack of people probably has something to do with the Gaurdian Genies and the Genie Realm having a hugely negative effect on the population, since we don't see a whole lot of humans very often, it may have indicated that something bad happened to a lot of them. #2 Some of the technology and craftsmanship that's on display, like Propeller Town on Pirates Curse, the giant airships that Ammo Baron uses in 1/2GH, or the large underwater passageways that you travel through in Seven Sirens. Some of the technology has this old school steampunk feel, some of it functions with the assistance of magic, and some of it is just extremely advanced technology that we can't utilize at this point in time.
Well, that's all I have. I just thought it would be nice to attempt and expand my knowledge of the Shantae universe by thinking about what time period it's in. I'm probably wrong but it was interesting to think aout anyway