Is this a sign that no one wants this type of app or is this a sign that they failed due to not enough people knowing it exists (bad marketing)?
Also, what percent of a startups (let's say app company) success is reliant on marketing?
You tell us. This is your niche, you should get to know it better than any of us do. Use the apps, see if they have issues. See if there is interest for a better app than what currently exists.
As for the second question as to what percent of an app startup's success is tied to marketing? The answer would be 100%. That marketing can be as simple as telling your circle of friends and convincing them to tell their friends, but it has to start somewhere. A basic website, reaching out to bloggers/reporters, telling friends and family, that is all marketing. Without some form of marketing it will never succeed because nobody will ever hear about your app.
Some products & markets require you to go out and get users more than others, and they may not have done that.
It's on a case by case basis, just be sure to get validation for your project. Make sure that you're making something people actually want, and if they want it, how much they will pay for it. Can't stress it enough how important it is to go out and talk to potential customers, ideally hundreds, and figure out if they'll pay and tell their friends about it.
Marketing is important -- having a good landing/marketing page, getting press, etc. But at the end of the day the product is what will create retention. Looks get the first date, but your personality is what will get you the 8th date.
Edison made thousands of light bulbs that didn't work before finally making one that did work. There are a great many ways to fail. Their failure does not necessarily indicate anything about the odds of your product. It depends on a great many factors. Given that you have not linked to your thing or theirs and haven't even told us generally what you are making, this question is just way too vague. And perhaps that is part of your problem generally.
This really depends on the vertical. Generally speaking, the less reliant on paid marketing you are, the better. Truly excellent apps market themselves. If you're entering into a niche vertical however, having to deal with marketing will probably be an unavoidable fact of life.
As far as competitors, it's almost always a bad idea to fret over the competition even if they're established. In this case they clearly aren't, so your only worry is whether to take heed of the fact that all of your potential competitors are basically dead on arrival.
As the other comments say, this really boils down to your judgement. Check out the other apps yourself, see how similar they are to your own execution ideas. If they're identical, you may have a problem.
Apps should be a freebie (not literally free in all cases, but cheap) that is merely a hook/marketing channel for your business.