Why is it so hard to get people to look at my original fantasy novel? Yeah, they'll look at my fanfiction, but my actually good fantasy novel they will not. At this point, maybe it's just time to sell my soul and write an isekai because my story clearly isn't interesting enough as is.
Ok, I just looked at your story just for a first impressions value. (Didn't read any chapters, and I didn't even read tags.) I can tell you just from looking at the cover, title, and chapters that you actually are doing a lot of things that can be improved upon.
Starting with the title, "Rip Current." It is not a strong enough title, it does not peak curiosity. You need something that sparks the imagination a little more like "20,000 leagues under the sea," for example. Even "Rip tide" would have been a better title, although I don't know how accurate to the story that one would be. "Life in the Abyss" might also do the trick, the area so deep under the sea that light doesn't reach was actually the original use of the term "abyss," so it could fit.
Your synopsis does not have a good hook either, and does not keep the reader's interest. It reads like a boring history lesson. Try coming up with something in the first 15 words of your synopsis that gives at least 4 pieces of information to your reader while also raising a question in their mind. I have given my first 11 words for my "Key to the Void" story once and detailed out how that does what I have described above.
"Asaren and Tiaren are the first Elven twins to ever be born." It tells you the names of the 2 leading characters, tells you they are twins, tells you they are elves, tells you this is a fantasy setting, and tells you twin births are usually a near impossibility among elves, and tells you they are the first to meet these conditions. That's 5 pieces of information. It also raises several questions. You are left to wonder if there is some kind of magical shinanagans afoot to cause this twin birth, and it also raises the question as to why twin births usually do not happen among elves. So, that's 2 questions.
The purpose behind raising questions is because it serves as a hook to keep the reader reading through the synopsis. The reason for packing in as much information as you can into those few words is because 1. 15 words is about the average reader's attention span. They will have usually made their decision on whether or not to continue reading by the time they get to the end of those 15 words. 2. The information you can pack in is an essential part of what makes the question to follow interesting. The question is the most important part, but the information you front-load it with is what raises the interest.
These first 15 words really are incredibly important in your synopsis, but the rest of your text is important too. However, if you have formed your first 15 words correctly, the remainder of the synopsis should flow out from that as a result.
And, the third thing you should REALLY consider doing is name your chapters. If you name the chapters, those chapter names will appear in the "last updated" section of the stories. This means that the chapter names can serve as another way for you to generate interest for your story.
So, it's really a lot more than just whether or not you have an "isekai" tag. If you have all these failures to appeal to the audience, even adding an "isekai" tag is not going to help you. Yes, it DOES help generate interest, but you have a lot of other opportunities you are not capitalizing on here. I think each of the 3 things I just recommended has about the same level of power to fan appeal as adding an "isekai" tag. Some of it may even be more powerful.